I take it that you are applying a dry cure and not injecting/brining the butts. If so, sounds like you know the answer to your own question.
I have my first two buckboard bacon butts curing in the fridge right now so I am not a bacon curing veteran but everything I have read suggests the fry test as a rule of thumb with additional soaking if too salty.
In terms of curing time, HiMountain Buckboard suggests minimum of 10 days. It depends on the size/thickness of the butts and how much you trimmed them. Mine were about 3.5 inches thick so I am expecting about 12 plus days to cure. As the cure draws the moisture out, look for a firming in texture as a sign of the cure progressing. Have fun with it
Recommended reading: Charcuterie by Michael Ruhlman