Whoa whoa whoa, you have sex?
That's not a "practical" relationship. It's romantic, emotional, and physical.

Marriage is basically just a ceremony, a ritual. Fuck it.
Unless you're talking LEGAL MARRIAGE, which is a legal arrangement with lots of fine print and legalese about assets and how they are shared, divided, etc.

The paperwork, the ritual, what is it? What do you really want? And why is it SOOOOO incredibly symbolic to you? Notice its not symbolic to a lot of other people?

People get married, people get divorced. The difference is that people who are actually in love stick together. You said that you want ACTUAL love because he's supposed to want to marry you. Hello? You're having sex and stuff, that's love. That's actual. That's more actual than marriage. Marriage does NOT make that more actual. Not one bit.

What you really want to know is if he's ready to go long term with you and spend the rest of his life together. So ask him that, specifically. Marriage is NOT part of that conversation. Period. Find out what you need to know without getting confused about it.

He's young, he's going to say stupid stuff without knowing the depth of it, like the marriage talk you had. You need to talk to him and explain point by point, what's serious, how serious, why serious. Also explain that he needs to be on a commitment path that has some kind of end point and destination, like being able to say how ready he is and at what time.

Try replacing the word marriage with something along the line of, "Are you ready to put a baby in me, because I will leave your ass if that doesn't happen within X years or if you're not continually on a path toward making that happen. It matters. Period."

Then give him lots of time to think about it if he hasn't already.