@ernpick1 Welcome to Mayo Connect. I salute you for being so caring and knowledgeable about your wife’s condition. Now you are wondering about wound healing. I found this article that says lots about wound healing, almost too much. If you scroll down to the last section, it talks about diabetes and wound healing.
https://sitn.hms.harvard.edu/flash/2013/issue133a/
And, yes, immunosuppressive drugs also delay wound healing. Keeping the wound open to air as much as possible is very important. As the wound heals and you wash it, be sure to not disturb and new tissue or scabs. Can you wife help at all? Are you or she able to hold the belly flap out of the way when she is up? Maybe the surgeon could ask for a home care nurse to visit your home once or twice a week. She could assess the wound and give suggestions.

Are you doing anything special to take care of yourself?