Question

Does a factual doubt—for example, whether a certain oil was used to fry meat—count as a real doubt if there is some way to clarify it, but doing so would be a hassle for me, or not? And if not, is there a difference between a minor hassle and a major one?
B: If, for example, I am careful to wait 6 hours between eating meat and dairy, and right now there is a doubt about whether something is meat-based,

and 3 hours have passed since I ate meat, can I combine those 3 hours that have already passed and make it into something like a double doubt in order to permit it, or is the custom treated as actual law and not as a kind of doubt?