It's been a while since I read it, but as I recall he was confident someone would figure out his identity eventually, and then it would bring (what he saw as) unbearable social disgrace on Cosette (and Marius). I also think Valjean's whole perspective was, 'A life with me is forever a life on the run. So I have one mission: Get Cosette to the point where she doesn't have to be with me anymore.' Once that was achieved, I think his whole perspective didn't even really stop to consider, 'Can I stick around?' The idea was, 'She is unburdened of me, now I can disappear.'

The 2012 film had its strengths, but it is not the same experience at all as the Broadway musical. But I'm not suggesting you watch the musical (though, I mean, definitely do if you get the chance), I'm just suggesting you listen to it (specifically, the Original Broadway Cast recording). You already know the story, so you should be able to follow along pretty easily. If you find you enjoy it, then I suggest getting your hands on the filmed 25th Anniversary Les Misérables in Concert, where much of the original cast partially acts out the musical while singing it.