Would Trump refuse to concede?

[Atlas Has Shrugged]

If it's 270-268 with her winning Ohio by a few hundred votes.

Anyone should refuse to concede in those circumstances, of course. Or at least do the Nixon and say "it looks this way but we're not sure/we'll figure it out later but you can go home, thanks" type of thing.

[Atlas Has Shrugged]

Even if he doesn't, it makes no difference. People never understand that a concession is not required for an election to be certified. He won't concede no matter how much he loses by, because he's not sane enough to do it.

Probably.  He has a reputation (and an ego) to maintain.  If he can "claim victory," he will.  No, it has no bearing on Clinton's swearing in, but he will go on insisting that he won the 2016 election until the day he dies.

So he'll be like Al Gore minus the hunt for manbearpig and the rape allegations?