I don't know if this can make you feel better or if I'm just commiserating with you, but when I had my RYGB 17 years ago I had to have an open procedure, 7" vertical incision from my navel to my sternum, and had to recover in bed for the first week post-op, then go back to have my staples out a few days after that. But my surgeon routinely takes the gallbladder at the same time, so no additional problems there. But it was very painful and I envied all the people who came after me and had the surgery the way it's done now.
I've been reading the posts here ever since I had my surgery and a lot of people just need a few days off post-op. To me it seems like a visit to the dentist compared to the way it used to be. Of course, your situation is obviously complicated. But I don't think you have a lot to worry about. Will you be under general anesthesia? I'm guessing you'll also be having an open procedure.
Sometimes, like you say, it stinks knowing what might happen. But maybe you should schedule some more time to find out how realistic your fears are. I haven't read many horror stories in this group, though it can be tough on some people more than others. Most of the members whose stories I've read recovered without a lot of difficulty. I definitely feel for you, though, since you have to go through at least two procedures because of the stones.
Maybe focus on the serious weight you're going to lose and the great figure you're going to have, the clothes you can buy, and the healthy new diet you'll develop and end up feeling like a million bucks! And make sure you measure your neck, upper arms, thighs, waist and any other place that will change your lovely physical self in addition to your health. I'm going to attach my before & after pix here so you can see why I was so grateful afterward.
If you look at all my pix, you'll see all the food I've learned to cook and bake using healthier ingredients, too. And the bonus for me was that I was able to go hiking and camping all the time, which is my passion now.
Best of luck to you. I hope when it's all over, you'll be so happy you did it because it will take away so many problems and pains.