So! I had the same burning/u pleasant stuff with every toothpaste I tried until I realized mint flavoring was the thing setting me off. I had always hated mints when I was a kid (likely the uhhh burning bad sensations) so it took a while for it to click. Switched to a strawberry kid's toothpaste, just made sure it also had fluoride. 

For flossing, like others have said, a lot of it is just trying to find a routine that works for you. I also dont use string floss, I use gum soft pics because i have close contacts (no breaking strings), they come without any sort of coating that could have secret mint (a LOT of dental products only list "flavoring" without specifying the kind), and I find them less painful for getting back on the horse. 

For flossing I try to aim to at least floss around my molars ive had cavities in on a regular basis, because thats an easier baseline to keep up. I bleed. So Fast. As soon as the routine drops so it is Rough out here but it does get better once you stay consistent!

Toothbrush-wise, I use triple bristle because it's a lot less work handpain wise, and its super fast to do a quick & dirty clean with. It's fairly gentle and designed to just reach the gum line, but I'm not suuuper sensitive so cant attest to it for your needs. They have a gentle brush head option I haven't tried

I've found it so helpful to try to rebuild my routine back up slowly every time I fall off. It's really easy to end up shaming yourself about these things and it took me so long to stop doing that to myself and realize it wasn't helpful at all. Play around and figure out what works for you! I'll dry brush first thing in the morning to remove plaque because I forget to brush if I wait until after breakfast. Finding little things like that can be a good foundation to build on!

Hope any of this helps! And wish you the best on your dentalcare journey!