White vinegar will pull alot of the smells and its also a softener. Kept having mildew smell when i went to high efficiency washer. Swapped to using distilled white vinegar and no more problems.

You are correct i should have stated use mold resistant board. I have had problems with standard mud cracking due to moisture in a shower areas. Thats why i suggested elastimer patch.

Get some elastopatch or some other elastimer for putty. If its an area that gets directly sprayed with water cover it with a rubberized coating like redguard or such. Should be good to go after that. I would suggest tile above shower surround to help wick off the condensation.