People can be in a solid relationship while still having life issues. Cloud has so many issues he doesn't know what to do with them, to be honest, and while I have a strong dislike with what they did with the relationship in AC, that doesn't mean they can't have a solid relationship afterwards now that Cloud is finally moving on from his issues. It's what we see in FFVII itself, though, that shows that Tifa and Cloud have a romantic relationship.

But yeah, I know of a lot of people who go through relationships where they love each other but one person has such massive issues that spending time with one another is not something they're gonna do.

Also, I know of real world relationships where couples don't share beds. In fantasy settings it's even more common for this to happen. I'm not sure I recall any couple sharing a bed in Final Fantasy, now that I think about it... Serah and Snow also have separate beds in Final Fantasy XIII, for example.

EDIT: Just read that in Japan this (two beds) is actually the norm.