What can be done to improve slow wound healing post-mastectomy? I've had 3 'revisions' since. I'm not diabetic; am a former smoker. Chemo is delayed

Radiation? did you have radiation to the area? This can delay wound healing. Otherwise, nutritional support with increasing protein in your diet may help with wound healing.
Warm soaks. After a mastectomy it is essential that one moves affected arm overhead to prevent a frozen shoulder. Here there is often pull on the suture line. In order to improve the rate of healing, one must have good blood supply to the wound. I have patients remove all bandages at home and suggest two warm showers per day, which enhances ingrowth of blood supply to wound and faster wound healing.