Reyes...?!? Looking to be spoiled a tiny bit...

return to the bar where he resides? There should be a follow-up conversation after the Sloane stuff. If you mean like much later in the game, then check out spoiler #2.

Yes, you will see him again in the end, but not with cinematic cutscenes. It's one of those "click and talk" type of interactions. Kadara was the bulk of his content.

He won't be there if you sided against him. You'll get an email from him, but that's it. You won't see him again this game. He's there in the bar where he always is if you side with him.