Good job on contacting him, you never ever know the reasoning behind these types of family 'events' until you hear both sides...or still one side, I guess. I am a HUGE genealogical researcher for our family (I know somebody else here mentioned their dad received a special recognition award for all his work), it is very addicting, and it is super fun for me. At 3500+ cm, he is definitely your father. I had thoughts beforehand of the exact scenario you wrote out was the reasoning behind everything, i've seen it countless times in my own research...well, a few at least.
I would make the best of it. You both will be new at this, so while you share DNA, you will still have differences. I'd try to look past those minor things, if possible, unless you find some other major things. If he is in the music industry, it would not surprise me him having a past with drugs and alcohol, unfortunately. It could be worse though, which i'm sure you could imagine.
Having pictures of your mother is probably not a bad thing at this point, considering she is the mother of his son. If it were some other lady, with whom he didn't have a kid with, it would be a little different....well, unless it was somebody famous I guess, lol. From an 'ancestry research standpoint,' it would be very common for people to show pictures and maybe documentation of their ex of whom they had a child with....you all are now shared history.
I personally felt that he did this in hopes that you may see it and reach out to him, much like he mentioned. As a dad, i'd be in the clouds if my son gutted-up the courage to contact me. I would not hold any grudge on what transpired 30+ years ago....let it be water under the bridge.
I'm not the most religious person either, but I swear these things happen for a reason. Whether the two of you hit it off like best friends, or an actual father-son relationship, it doesn't matter, just make the best of it. I say that cautiously though, because like I mentioned earlier, if he is some criminal or something worse (i'll refrain from listing), then that is different.
Brother, we are all different, but if it were me, i'd be very excited, even though i'd still be kind of weird in the head with it all coming in at once. Take it day to day, week to week, and year to year at a time.
He may be as freaked out as you, just remember that, even behind any excitement and joy. If he's never been a dad, then he will be new at all this as well.
On the flip, you may have some half-siblings!
Keep us up to date on how all this transpires. Be calm and don't make any knee-jerk reactions.
Regards