I feel like it's also possible, instead of explaining why He Can't Go Backwards, to make it a really costly or even just less useful thing to do.
For example, let's say he can rewind and fast-forward time around him, but can't actually affect himself. (For starters, he might look weirdly older than he should, on account of using his power to sleep in over and over again and ageing just a little bit more than everyone else...)
But what if things that happen to HIM aren't undone when he moves time backwards? So if someone stabs him, he can't just rewind and not be stabbed.... he'd rewind and then be back in a different point in time, carrying the stab wound back with him (a la Echo, short video). What if he can only travel forward and backward across the amount of time he's been alive for, which cuts down significantly on the things he can affect? Plus, he has no spacial powers -- if something catastrophic happened, and he found out about it and wanted to stop it, he'd have to (a) go back pretty far in time, (b) skip whatever he had originally been doing that day, which changes history significantly and might not be something he can afford to do (c) somehow get himself into a position where he can change or influence or convince someone to stop the catastrophic thing.
If you make it harrowing and complicated and SHOW that it's harrowing and complicated, then we won't see time travel as an easy fix. We'll probably want him to try, but if we've seen going back in time mess things up before, then there could even be times where a character asks him to go back in time to fix something and the audience is yelling "NO!! THATS A BAD IDEA DONT DO IT!!" It could be a really interesting element of the plot if it's something you would enjoy working with.
ALL OF THAT SAID, if you feel like that would distract from the story you actually want, then I'd go with option one -- just go ahead and say it can't be done, and we'll accept that it can't be done. If you have a character who has a power but is afraid to use it because What If It Does Something Bad?? then we're going to be waiting for a cross-the-streams moment where he uses it anyway, so if you don't want it to come up, then I think it's best to just say it can't be done.