It's all got to come down.
Any form of drywall behind tile in a wet area is going to fail.
You really need to think about picking up a book on tiling or at least doing so more reseach before doing any more.
Tile is a one shot deal, done wrong and it's trash.
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17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?