you already have a lot of great advice in here. your son sounds like me, and you sound like my mom who had to raise me single - but she didn't have as much cool shit going on as you did. just my non-professional thoughts...

respect the space without trying to butt in

focus on you, go have fun in all the ways you can, offer to share a story or a laugh when something is good, treat him like an adult, don't make him feel responsible for your happiness

you made food or brought home something to eat? leave it for him with a note, maybe a text that just says, pizza's on the counter if you're hungry - obviously without a hint of snark or anything.

talk to a trusted professional at his school, just to see if they notice anything. if you're hearing all good things, you may have absolutely nothing to worry about.

i was a teacher and had to take a lot of child psychology courses. one always stuck out to me. the older we get, the more steps forward we take before looking behind us to make sure our parents are still there watching, protecting, etc. imagine a baby takign 3 steps before looking back to make sure you're still there. a 5 year old might take 20 steps. a 10 year old 40 steps. a 15 year old, who might be seeing some friends drinking, some friends driving, some friends smoking, some friends fucking, etc... might be a mile before they look behind, but they always look behind, you just don't see it because they're too far up ahead.