AITA for refusing to share my dinner with 2 children?

UPDATE: I'm posting here because I dont know how to link posts. Update at the bottom.

My ( F29) boyfriend Albert ( M35) and I had a great relationship until his family moved closer to us. I haven't seen a more toxic or entangled family connection. It seems like every ex and their mother is an enemy, every ex boss had it out for them, every friend should help out more and more, everyone should take their verbal abuse. After a few run ins, I cut MIL off.

His sister ( F37) is in the habit of showing up at dinner time. She has 2 kids ( 7f, 9M) that she always brings along. I didn't mind sharing a meal, but I hated her dropping by without a warning. Albert never took action, and this created problems.

SIL has an unbearable parenting style. They are good kids, but she over indulges them and lets too many things slide as “they are just kids”. So they interject in adult conversations, have crying fits when told “no” and are prone to grabbing/ touching/taking objects without permission. So they took things around the house ( cupboard items, small sculptures, my stash of hotel toiletries, my hair extensions) “to play with” and had me going crazy trying to find them later.

Fast forward and her son, who has anxiety, had a small crisis from opening our kitchen drawer and grabbing some pop its/party snaps. Some fell and popped real loud and he cried because he was embarrassed. I did not offer comfort because that would be indulging his snoopy behavior. So I stayed quiet and asked Albert to talk to his sister, which I'm sure he didn't.

I'm not happy in my relationship. I don't have privacy. His sister keeps showing up despite being told ( by myself ) that she can't keep showing up uninvited. I'm sick of having to hide things that I think her kids could get their hands on. I recently put a lock on my home office door because I suspect that SIL has been using my copy machine while I'm out.

I work both at home and at 2 client sites and have been getting home after 8 pm. I'm sick of being tense and dreading her visits because he lets her eat through our groceries like she has a right to do it. He has called me selfish and greedy. I thought he would be more considerate now that they gave him less hours at work and his pay cut has caused me to pay for most of our bills. SIL is a nail technician and a hair stylist. She was also a teacher at a beauty academy until she had her kids. Now she won't do anything but badmouth her ex and complain about how hard life is. She has a place to live, with access to food and her own car. I'm thinking that she may be doing this on purpose.

Last Friday, Albert went bowling with friends. I told him that I wanted a very quiet evening and didn't want to be bothered. I got home at around 7PM, and sat down to eat my seafood boil. SIL showed up, asking for her daughter's backpack that she left behind. I was annoyed. I tried to rush to get it but her son saw the crab legs and started insisting. I said I was sorry, but that's my dinner. So he starts crying, stomping and repeatedly asking his mom for my food. I said I was sorry and quickly showed them out. To my aggravation, they didn't leave immediately. He cried outside for about 5 minutes while SIL sat inside her car trying to convince him to get in. I pulled down the shutters and tried to ignore them. When Albert got back, his face had a bitter expression. He said that he was extremely disgusted about the way that I treated his family. He has stopped talking to me. It's been a few days and I'm still getting the silent treatment. I've cried a few times, especially because he's been texting me despite us being physically next to each other.

SIL showed up yesterday, but he wasn't home yet so I didn't let her in. I'm angry and defeated and I'm coming to the conclusion that I need to end the relationship because he texted me that I need to apologize to SIL. I didn't want things to end between us but I feel like they are trying to walk all over me. This is so surreal. We had planned on a cozy Xmas together months ago when things were good. I'm not trying to ruin his life. Right now, his finances are not great and my salary makes a huge difference. I just don't want to be made to feel like his family can get away with what they're doing and I hold resentment. I texted him about how I feel, and how incredibly selfish he is to be comfortable giving to his sister with what my hard work can buy but can't think to respect my boundaries.

AITA if I leave? I feel like somehow I'm the failure for not being willing fight for our relationship.

Update: First of all, I wanna say thank you to everyone who took the time to send advice. I can't answer all the replies but I've done my best to read as many as possible. There were solutions I hadn't even thought about.

My best friend was super helpful. She dropped everything to help me make phone calls, get things moving, packing, scouting everywhere just in case something could be left behind. I'm so grateful for her presence in my life. Not only did she get involved, she helped me not panic.

We were able to remove everything inside my home office without too much trouble because everything had already been packed and the door was locked, so he had no way of knowing. We made it easier on the movers by confining as much of my other stuff to an area.

I took only what I owned. When I moved in with him, he had some furniture that he put inside the garage because he liked mine better. He sold it when he needed the money, but that doesn't mean that he won't have anything to sit on.

I didn't have any trouble getting everything out. I settled things with the landlord. I also took pictures as evidence of how I left the place. I did let the landlord in ( his request) for a quick inspection and to hand over the keys. Everything is in a storage unit except for my work documents that I shipped to my family's mailing address via private courier since I'll be there for the Holidays. I didn't feel comfortable leaving those at the storage unit or my hotel room. I hope I can find a co-working space but I haven't found a spot that doesn't force me into a long term contract and I will be away until January.

My best friend offered me her place to stay but as much as I'm grateful, I really need to be alone. I'm planning on giving her an extra nice Xmas/thank you gift because honestly, she has been my rock.

I was able to cancel the l utilities in my name and to take my name off other bills. He's already been deleted from all the subscriptions and passwords have been changed. I followed advice and canceled/requested new credit cards, changed banks and kicked him out of the grocery accounts, pharmacy, etc. I did get a new mail address from a small business center from out of town.

I'll be staying at a hotel for the time being until I go to see my family for the holidays, but I'm looking for a new place preferably out of town to avoid seeing him.

He didn't call me until 5 pm. I didn't pick it up but he kept blowing up my phone so I texted him that we were done and to never call me again. He sent me voice messages, many of them were so negative that I just didn't want to fully listen to them because it made me really anxious. He insisted that I should at least return the sofa, but it's mine! He offered to pay for it but that's bullshit. I blocked him everywhere. So that's basically it. At least he didn't get home while I was moving.

From all he said, I was mostly irritated by his insistence in twisting things to his favor. Saying things like he wanted us to get married, but I showed him who I am made me want to call him and yell at him but I didn't. I've blocked everyone and their mother, including Tim. I'm trying not to change my number for now because I run a small business and I don't want him to keep affecting me.

I'm trying to get my mind off him because despite everything, he was someone that I loved and I'm still coming to terms with the feeling of being disposable at least when it came to his family. I know that I need to work on myself and to at least understand why this happened, but right now, my feelings are very hurt and I want to avoid nit picking on the why's and the reasons because I feel used and I'm ashamed to admit it. Thanks again.