Hi Griffin
16ac Very hard is HH for very hard pencil. The first H is a theme letter.
14d is two words - 3,8. The definition is outside. It's not a theme word.
I'm down to my last five!
43ac, 47ac, 48ac, 44d, 38d and 26d (well that makes six) Five of them must be theme words unless I've made a mistake somewhere else.