Would I benefit from a belt lipectomy or tummy tuck?

your best option is to have an evaluation by a Board Certified Plastic Surgeon, or a second opinion if you need more information
We have performed over 100 Around the World or Belt Lipectomies, they have the ability to smooth the Anterior Abdominal Wall, tighten the abdominal wall musculature, correction of the flanks, and an elevation of the buttocks.  Actually, it was the first type of Buttocks lift.  Check out our website for results to see.

The body lift is designed for patients who have a lot of loose skin in the buttock and lateral thighs. I think most of your trouble could be corrected with a tummy tuck. You could also have some liposuction and possibly transfer that fat to your buttock if you would like to firm it up a bit without the big posterior incision. Good luck.