1. First of all, don't let their opinions make you falter. Yes, some people DO fail. However, most of the time that can be traced back to them getting back into bad eating habits... i.e fast food, drinking soda again, eating cake, cookies, ice cream, and massive amounts of bread and pasta. And statistically ANY surgery can cause nerve damage not just weight loss surgery. It depends a lot on your own body, how many other prior surgeries you've had, if you have nerve disorders like different types of neuralgia, Fibromyalgia, etc.
2. I read up on statistics when deciding on my surgery and Gastric Bypass has a 0.14% chance of mortality in the operating room (essentially 1 in every 1000 people), 1% in the first 30 days and 6% in five years. However, you have to think about the fact that many of us have been overweight for a very long time and it takes a toll on our bodies which is likely the reason for the 6%. Some people just waited too long to do anything about it. Avoid NSAIDS like the plague though because once you have Gastric Bypass that causes massive bleeding and you'll land yourself in the hospital. No ibuprofen or asprin for you! (though you likely already know this lol)
And I TOTALLY understand the facial pain! I have TN (trigeminal neuralgia) and it was misdiagnosed for YEARS which means it didn't get the proper treatment and led to it getting worse and worse until I was in constant pain for MONTHS! I couldn't sleep, couldn't eat, couldn't talk because of the sheer amount of pain I was in and I would cry myself dry. I was exhausted, in agony, miserable and desperate to find an end to the pain. I would literally go to work and cry while I worked. I had brain surgery in 2017 and it had a similar mortality rate to the GB surgery and had some other rare complications and even some common ones. I was at peace with whatever happened. If I was one of the rare 1 in 1000 that died then it'd be an end to the pain, if I was one of the other 999 people then I had a 95% chance that the surgery would work for me and a 5% chance that it'd do nothing to help me. Even then, I knew it was just a temporary solution since TN has no cure. And it did work. For two years. The pain came back last year, but the surgery is amazing in the fact that it's kept the most debilitating type 1 pain away. I have atypical TN (which is apparently rare) and have had both type 1 and type 2 pain. I had the surgery because the type 1 pain is like being stabbed repeatedly in the face with a scalding hot poker where it twists and twists and twists and then repeats. When I have flares I only suffer from the type 2 pains now and hope that the type 1 never comes back! Also, I haven't had a flare since August!
I hope that everything goes well for you in your surgery and I hope they can eventually figure out what's causing your other health issues so that you can get the necessary treatment without those issues getting worse. I wish you the best!