Aside from the creepy age gap, at worst he should be asking you to be his girlfriend and be in an official relationship for a period of time before you start ringing wedding bells.
The fact that he's so eager to marry you without even wanting to date you properly first says a lot, specifically that he's only after one thing.
I'm assuming you come from a background where pre-marital sex is frowned upon, all he wants is to have sex with you - marrying you ASAP is the only way he can get it.