This is for Couplet:

Wasn't that tree-demon made out of wood? Thus, piercing Angel's heart with that branch-arm should have dusted him.

Did it hit his heart? I think it was more in the center of his chest than to the side

There was a bit of dialog where Angel asked Gunn if the demon really was wood, and Gunn said no, he was flesk. He just looked like wood. That's when Angel knew it was safe to taunt the demon and sour its feed with his his vampire energy.