It should not have been a surprise to you he didn’t want to get married. You don’t know him well enough.
Believe or not men have feelings too and as you well know we don’t express our feelings. Men would love to express our feelings but we don’t want to be judged and or corrected. The man gets to talk about his feelings for about three minutes before the women interrupts and wants to make her case. Or a man is told his feelings are just like a man and outdated in today’s world. Whatever he says will be taken out of context and ridiculed. We know that so we carefully manage what we say so we don’t get you upset. A man learns that TMI too much information is bad so he lies about what he really thinks.
Appreciate what you have with him. Ultimatums never work and you will lose what sounds like a good relationship.