I tend to ignore statistics, because they can bend any which way. But what I notice is, you aren't *sure* this is a good idea. Such a big decision, I wouldn't do it unless I was sure. Moving out again would be a pain. If she's the right girl for you, it'll work out whether you live with her or not.
Maybe this is just hard because you're trying to decide right now. Even though waiting to decide might feel like being up in the air & uncomfortable, so much can happen in 8 months. Whenever I try to decide something for a time so long in the future, things always change anyway, so the decision changes or ends up not mattering much or else being really easy. If you just keep going day by day til more time has gone by, I bet your decision gets clearer one way or another.
Is your dad or your GF wanting a decision right now?