The "Hair loss" is called Telogen Effluvium
https://www.webmd.com/skin-problems-and-treatments/hair-loss/effluviums#1
It's not really "Hair loss" it's just a larger % of your hair follicles going into rest at once, so when they reactivate they shed the hair they were holding and that gives the appearance of "hair loss".
Fear is normal, NSAIDs are not the only pain relief out there, there are options. Pretty much everything you've listed is normal fears, and pretty much, all of those fears, you'll laugh at down the road.
I was 370 at my largest. I'm 210 now, I have some extra saggy skin, but it's really not THAT bad and it's totally hidden under even decently tight clothing.
Just remember, staying overweight *WILL* kill you. If something was to happen during your surgery, the best place for that to happen, is in a hospital.
No one but you can tell you if what you are going to do is right for you. You have to make that call. Weigh out all the pros and cons, and make your decision based on that, no one is going to look down on you for making the best decision for your life that you can.