Break in depends on the engine type. Running an ABC engine rich will cause quick wear to the sleeve and a loss of compression, but a non-ABC engine HAS to be run rich for break in.

I agree with the wing issue. You really shouldn't use 5 (or 6) minute epoxy for anything that requires time for alignment etc. If you read the fine print on the bottles it will probably say "Working time 2 minutes", "Sets in 5 minutes". Working time means that's how long you have before it starts to set, and as you discovered, once it starts it's nearly impossible to continue.

You'll probably have to cut the dihedral brace, then use a dremel or some other tool to remove the hardened epoxy from the root ribs. You could wither drill out the dihedral brace and try to make up a new one to fit, or epoxy the halves together. But you should then wrap the joint with fiberglass and epoxy that as well.
Dennis-