Can I Have Spinal Fusion and Tummy Tuck at Same Time?

This combination does not make sense on a number of levels-
Safety- the prolonged anesthetic time and significant risk for DVT and pulmonary embolism make this combo a no-go in my book.
Logistics- For the trunk and abdominal skin excess that you describe, you would require more than a simple TT- a circumferential body lift on a spine patient would be out of the question.
Cost- any cosmetic procedure done in a hospital setting is going to have an excessive facility fee associated with it. Its for this reason that plastic surgeons have largely abandoned hospital-based operating room for more efficient and convenient ambulatory surgery centers. Not sure if your spine surgeon operates out of an ASC, he might, some do.

It would be my advice to focus on the spinal fusion operation at this time. Having lost that much weight, you are more likely to benefit from an extended abdominoplasty or circumferential dermolipectomy procedure. The risks of a combined procedure of that magnitude are significantly greater than if performed separately, in my opinion.