If you're not ready for all of this. You're not ready. Tell him that you're not ready to get married and he'll have to wait. If he loves you enough, he'll wait. If he doesn't want to wait, dump his ass. If you're in the relationship for only pleasure, you should dump him. Dating is to only see who is right for you, not a game.
No I don't think you should as you never know you might want more later on when your ready, just explain how you feel when it comes to a marriage and if he sees your point and feels he taking it a bit far he will wait but if he not just dump him straight away, your not his toy to be push when he wants it to and your life isn't all about him and what he wants
Only one hard and fast rule for this situation---complete honesty. It's his choice if he wants to hang around and see what happens, but be honest and make sure he knows at this point, you like his company, but you don't see an intimate future for you two.