Coincidentally I did actually give Emboar Sucker Punch in its moveset, and I suppose you have a point with Payback. As it is it's a bit late to change to Fire/Dark at this point considering I'm intending to release this very shortly, but maybe I'll consider it for a future update or something.
Also, Foul Play would be pretty bad for Emboar seeing as it makes its own Attack stat useless~
I don't really like the idea of Fire/Normal, particularly because nothing about Emboar looks remotely Normal. I'll admit it doesn't look to Groundish either, but Pignite really does to me.
Also, that tidbit about Emboar's origins with water are interesting actually. That might explain why it can learn Scald!
As for Struggle Bug being 80 power, it IS very strong, but I really wanted it to actually be useful. Burgh only has two Pokémon that can properly utilize it regardless, so you'll mostly be able to use it for your own needs.
The level curve means your Pokémon will be about Level 30 by the time you get the TM, so I don't think it's too problematic.