You've gotten some good input, I'm just going to throw in a few more pennies.
You already had the discussion about wanting to be engaged before a year of living together came up, that's a perfectly reasonable boundary, which is why he agreed to it. Now, without getting into the studies about how living together first doesn't' necessarily guarantee marital bliss (then again, nothing does), you went from living together to 'engaged' to 'after we're married in *one* sentence. That would freak anyone out. Really, it would.
Couple of things: It's *awesome* that he opened up to you about his fears of marriage, it truly is. If he's never seen a happy one, he is justifiably scared because he has no role model to gauge himself against. Although I personally don't require it, marriage doesn't scare me because I see in my parents' 41+ -year lovefest what it takes to make one work, good times and bad. But not everyone is so lucky like that, so let's try to understand where he's coming from first before hanging him out to dry. One way you could assuage those fears of his is to work on making your relationship with him really great. Communicate, keep that open line going, discuss fears, hopes, joys, sorrows, and keep an open mind and an open heart. He will come to trust that more and more over time. If you let your own fears about his fear of marriage now, then it *will* affect how you interact with him, which will in turn affect your relationship with him, which will in turn only serve to bring all your fears to life. Make sense?
Since you've made the one-year mark the litmus test, which again, is perfectly fine, then I say keep quiet about marriage, engagement, all of it, until that one-year mark actually hits. He agreed to it before and as a condition of you moving in together, so he can't cry foul later on. Don't even hint about marriage, that's low. If on that one-year day you are not engaged, then you, being the caretaker of your life and your soul, KNOW what you need to do at that time. If you don't, then how is he (or you, for that matter) supposed to take you seriously?
Women who stick around forever waiting and hoping for the engagement ring and the commitment that never comes, have set themselves up for that all along the way, make no mistake. They do so by not setting realistic limits, not knowing or saying what they want, hoping things just magically change, not taking things at face value, but mostly, they do this by not setting personal boundaries that *they themselves* respect and pretty soon, they've invested years and years into something that was never going to be. That's key: You can't expect anyone else to respect your boundaries if you neither set them nor respect them yourself.
The way to avoid waiting around forever starts by doing what you've done, which is state clearly what you want, and then let life unfold in its own way, joyfully with a realistic boundary. Once that boundary is crossed, then you act in a way that protects and honors you, meaning, you love yourself enough to walk away from a situation that will be ultimately hurtful to you or dishonors you. THAT's how not to wait for years.
In the meantime, work on making your relationship with him the best it can be, you both deserve that.
Best,