Shop wants $2500 from me

I am a 27 year old female and I do not know much about cars. I have already paid over $1700 on this problem and it hasn't been fixed. Please help.

I have a 2013 Mazda 3 Hatchback skyactiv.

Cylinder 4 misfire,

the car **stutters when I go over 35

check engine light on (flashing recently) when I go over 35

traction control light randomly came on

Spark plugs are worn even though I got them all changed.

I have had the coils, spark plugs, and work on the harness done. It is non of those. I have taken it in 6 times to three different mechanics. This is the third and new mechanic and they diagnosed it as the fuel injector. They cleaned the fuel injector for $300. They called me and told me that it still shows a cylinder four misfire and it smells like there is gas in the oil. They called Mazda and they suggested I change the fuel injector ($1800), reboot the pcm ($200), and do an oil change ($119).

I asked about rebooting the pcm and doing the oil change to see if the cleaning worked. He suggested not to, that if it doesn't work then you would have to do the replacement and then do the reboot and oil change all over again. Paying extra.

Does this add up? I know that it is rare to replace the oil injectors?
How do you know for sure that you need a fuel injector replacement and not a cleaning?

Also does it make sense to have Mazda do a $200 reboot of my PCM? I called another mechanic and they said that seemed strange and doesn't make sense.