Back for More Time

If you think about it, Marty McFly actually had more time to fix the timeline than he believed. He thought that he had to do it before the people in the picture faded, but he probably could have waited till the physical photograph disappeared completely. If he hadn't fixed things, then the picture wouldn't have existed in the first place because there'd be nothing to take a picture of.

Bonus Question! 

Michael J. Fox versus the fantastic Mr. Fox?  

 I personally prefer Michael,  but if it's a duel of charm, I've got to give the win to the mister.