Hi, I don't know what I can say to help you work through the anxiety you are experiencing, but I wanted to try. I am a trans woman married to a wonderfully supportive woman. We've been married for 35 years. She has been the bedrock of my support since I began my transition 3 years ago. The surgical procedures that I have undergone over that time are many, including facial feminization surgery, sexual reassignment surgery, breast augmentation surgery, a full face lift, and others of a lesser nature. In each case she has been there to take care of me and make sure that I did what needed to be done before and after the surgeries to get the best outcomes.
These surgeries were performed in the USA, Spain, and even as far away as Thailand. Never once was there an incident that we are aware of that put my life in danger. Not once did I suffer post-surgery complications, unusual levels of pain, unpleasant reactions to medications, or anything of an unusual nature. Of course we were careful to select reputable professionals working in modern up-to-date hospitals and certified surgery centers.
I was so fortunate to have my wife with me at each location, close at hand, even staying with me in my hospital recovery room overnight after my FFS procedures. It was not just a comfort to me, but also made it easier for her, knowing what was going on rather than being left alone to wait and worry.
I want to reassure you that the advances in medical/surgical technology have lowered the risk of these surgeries tremendously. Your surgeon has likely performed hundreds, maybe thousands of these operations without incident, and knows how to achieve very good results.
I will tell you that at my latest surgery just a month ago. I was so relaxed, I could have been going in for a teeth cleaning. My wife, too, felt confident that all would play out as planned. A certain amount of anxiety is natural, but there's no reason to let it overwhelm you.
As far as worries about the future of your relationship, my wife will admit to similar worries, as do I. We promised to talk about our feelings regularly, and to be honest about everything that was happening even if the news was troubling. It's certainly possible that post GRS, things could change in certain ways. It's not unusual after GRS to wonder about what sex would be like with a man. I've thought of it myself and told my wife about it along with reassurances that curiosity is not the same as desire, and desire does not mean acting out those desires. Our love for each other is too strong to be destroyed by such shallowness. Instead we have found new ways to be intimate and to meet each others needs at a sexual level.
Think positive thoughts, vrt. Don't dwell on worst case scenarios. The probability of everything working out perfectly is very high. Really.
Good luck and all the best.