Can't help you with question 2, I could surmise, but I won't. I imagine when the comb gets old and dark you will want to recycle it. (Okay, I did anyway.)
Regarding PT, I don't know the chemistry (I wouldn't believe it anyway), but I use it to border my landscaping and the grass won't grow next to it. What does that tell you?
Personally, I don't even like plywood. Hard on tools and exterior (or marine grade) is pricey. Besides, I think the bees prefer a "rustic" motif, think "shaby chic".