I've had male bettas with male guppies before without a problem, it all depends on the bettas temperament. If he isn't compatible with other fish might I suggest getting a nursery net and having him in that(inside the 55) instead of putting him back into an unfiltered/unheated bowl. I would also opt for just one angel if you have to have one. Also African dwarf frogs are quite social with their own kind and getting more then one would be better. If you really want a pleco I suggest getting a bristlenose plec.