Dude, no matter what, never snoop around. Just do not do it.
You need to ask yourself, what is it that you
really want to know:
Is he gay or bi?
or
Is he interested in being your BF?
For some reason, you seem to be concluding that, if he is gay, he will be interested in being your BF.
That just does not have to be always the case.
There are many guys out there, who would have no problem in dating another guy, but are not into coming out, admitting to anyone that they are gay or doing any of the gay stuff, whatsoever.
For many people, being homosexual and being gay are not one and the same thing. See, he might be interested in m2m sex (all that m2m porn). But he might not even vaguely consider the notion of letting anyone know that he is into men, or that he would openly wish to have a bf, date another male, live a 'gay lifestyle', frequent gay pride or even enter a gay bar., etc.
Ask yourself if you are looking for a BF, who would be reasonably out, just the way you are, or are you willing to go deep 'undercover', do the 'friends thing' and run your own affair behind the closed door?
---
Yet another thing: You say, you are close; you are very good friends, you spend a lot of time together. You are both young guys. Hasn't he noticed that you do not have a GF, that you are never talking about women? Being such good friends, haven't you managed to talk 'sex' yet?
SC