will we last

Fating? Haha but seriously does he only say that when he's frustrated? Or does he mention it more often? I personally dated a girl that was 5 years younger than me for a year, and she would get frustrated about issues I gave her advice that I've previously experienced. She felt frustrated that I didn't see it her way (even though I did. However my views on certain issues were different since I already had been through them.) I suggest that you two sit down and talk about it. See how you truly feel and if one of you has doubts think about ending it. My ex didn't talk and eventually it caused her to cheat, and then leave for another guy. I would hope something like that wouldn't happen to you, but don't think it's not a possibility. It can happen.

this kind of thing is really tricky, and only you and him can decide weather or not it's worth it. but you both have to have the same attitude of "lets just enjoy it now" for doing that to work. if you need to vent/talk feel free to send me a message, im here to help.

It's like a domino effect. If one person has doubts, the other starts having them too. I think you guys really have to reach inside of you and know if you wanna stay and be with each other.
Like really.
Take your time and think, both of you.
If you both do, well and good. and tell him to never say that again and sow new seeds of doubts in his head and yours too, which is pointless and erodes relationships

I, personally think age differences are good. And you should take it as a plus. Since he has gone through stuff, trust me, take his advice on issues. Do listen to yourself but also listen to what hes got to say.
And instead of turning it into a bigger deal, just focus on what you have and try to see things in a positive light. And enjoy the time you spend together to the fullest!

if you really want something you got to put in your efforts. But it's futile to do so if the other person doesn't want it. So talk it out. And see what unfolds. And know when to let go.