Incadescent does heat up really bad! My mom got me a tank off of craigslist for a QT tank and it has incadescent bulbs. I don't use them except at feeding time, and if you leave them on for like half an hour that top is HOT! You can actually see where the top is malformed I'm guessing from the heat.
Anyway, I think your new fish is fine. He was probably just a bit overfed and stressy. My rescue betta used to look like that as well and now his body is a deep navy blue color as opposed to pale grey, and his stomach is a lot more streamlined.
As far as bubble nests go, I have one (Prof. Lupin - rescue betta) who builds them all the time and makes his like an inch tall, my new little girl who scatters bubbles all over the surface of her QT tank, my new male who built HUGE bubble nests for like a week and then just stopped although he still does scatter them on the surface, and my old rescue betta Flame (RIP) who would build nests pretty regularly, but most often would just cover the surface with random bubbles. So, I think it all depends on the betta and I wouldn't worry if you have one that doesn't build nests every day as long as they appear happy and healthy. Although it certainly is rewarding when they build you a huge one!