I’ve had a lot of the same issues. With rapid weight gain we put a lot of stress on our bodies. At this time last year I hit 260 for the first time ever, and I couldn’t tie my shoes without breathing heavy. I was also snoring a lot and struggling with sleep. This year I hit 275 and I’m handling everything pretty well and here’s why:
I try to use low impact aerobic whenever possible. Walks with the family, eliptical trainer, etc. I powerlift so when I’m doing ancillary work, I use supersets to try to get a little bet of volume and anaerobic training in. I have also started playing a little basketball once a week.
The sleep problems are probably based on the increase of weight and fat, especially to your face and neck. It can impede breathing. The same can be said for the lower back pumps. Your body is just trying to adjust to the weight it’s being asked to carry.
Like I said, last year I got to 260-65 and really struggled. Now I can go more and stay comfortable, and when I “drop” to 260 or so, I feel really great. Good luck!