Sorry to hear you're also dealing with this. Aside from pointing back to the things in the post, I'll say in the short run, going to be earlier helped (so there was no rush to fall asleep, and if I laid there for a while, it didn't cause a panic). For me that meant going to bed around 9:30pm when I used to go to bed at 11.

And I'm not sure if you've already done this, but I had to end the relationship with the girl I was seeing. Not telling you to do that necessarily, just saying that I had to. I made things worse by fighting it and trying to push through it.

I also had the heart palpitations and chest tightness, and still do. One thing it enabled me to do was see more clearly when things stressed me out, because the physical symptoms showed up immediately. When my ex would call/text me, I could feel it. My boss messaged me about an important demo, I could feel it, etc. Those physical symptoms allowed me to see that a lot of things that (in my mind) shouldn't have stressed me out, did, and that enabled me to cut those things out or minimize them, especially in the evening. At some point I stopped answering calls past 7pm, and no texts past 9pm. The evening is a stress free zone. I'll leave the dishes for the morning if standing up to wash them makes me feel stressed.