You could look into baby led weaning, which is basically offering those foods in a form that requires him to lick it up and feed himself. Maybe go back to just the other two foods he didn't react to, and let him dip his fingers and "play" with it a little and see if he gets interested in actually getting it into his mouth. The mantra of "food before one is just for fun" is a reliable saying. Until age one, solid foods aren't a source of nourishment as much as an opportunity to explore textures and tastes, and to begin participating in the family's social customs around mealtimes.
If it were me, I'd back off of everything until the rash clears and then introduce the safe foods again one week at a time to watch for reactions.