ppkk, Whey you are ready to join the wing halves together, apply the epoxy to wing roots as needed and, like you said; in between the tab's broken pieces. Use Wax paper on the completed tab assembly and clamp together. 30 Minute/slow cure epoxy is best for wing half joining. Allow a day to cure then file any excess epoxy away for a properly shaped mounting tab.

Glass tape the center section to help prevent "wing folding".

Plywood offered today on some of these planes reminds me of a ham sandwich! The middle ply material IMO has just enough body/strength to hold the outer sheets apart, allowing the finished product to be classified as plywood.