have a serious sit down with him before you go forward, be open with him so that he can be open to you... if you can't tell/open up to him about your insecurity about long term relationships, then how can you see yourself being with him ?
second, ask him how does he truly feel about his ex? if he can bring time back, will he fix things between them ? if the answer is yes, then yeah his ex is a huge deal for him still...
if he wants to commit but no titles, can mean many things ... the moral is that he wants to commit, want you to be there, but maybe afraid to put titles since his ex sorta just left him
and you shouldn't shame yourself for not being a relationship expert... maybe it was never your priority, while partying was your thing, some people are the complete opposite of you, it's how we're made