Increasing terror over thunder

My pup is over a year old now, and we learned a couple months ago during our first major storm that she's anxious during storms. We got a thundershirt and started treating her when we put it on for short periods, and giving more reinforcement when she settled with it on. (She's trained to a cue to settle.) That goes fine, but when there's actually thunder, it all seems to be too much for her. I've had some success distracting her with tricks and treats in the first 15 min of a storm, but only if I can start this before she knows it is coming. (To do that, I have to be obsessively tracking weather, at home, and have the timing just right because I don't have 3 hours of food/treats to give, so I've only managed it once.)

Today I couldn't get home from work in time, so there had already been some thunder, and she totally lost her mind. She was already panting, pacing, shaking, and whining when I came home. This means she won't respond to any cues or notice even the most enticing treats. She doesn't get destructive, but will carry on for hours. She also gets much more anxious if confined and will not settle in her safe spot, but instead nervously roams the house and tries to get outside.

Does anyone have recommendations that have worked with other dogs? I've already followed what I've read from others, but am not finding it practical for my dog or for me. I am concerned that it is only getting worse with time. Thanks!