I failed the strength check despite being a paladin and using inspiration. I never saw him again even after getting through nearly all of act 2. I’ve asked this before, maybe even in this community, but no one gave a concrete answer, likely because the game was still new.
Only tangentially related, but if you choose to ignore the portal you can come back later to get Gale. I was in a role-playing mood on my first playthrough. When I encountered a strange portal, and was given only the choices of ignoring it or sticking my hand in I thought, “How about no.”
I missed both Gale and Astarion for several levels and thought the companions you got were RNG