I am the result of a mixed marriage that is still strong (40 years this year), so I’m not one to say it never works, but then, neither of them were really into faith discussions in the home, so that avoided a lot of drama. If either of them had been more devout, who knows?
I also wouldn’t put much into his past. It’s great that you waited for marriage yourself, but eliminating all non virgins will seriously limit your options, even at 28. There are many people (men and women), who are able to wait for marriage, but they often marry earlier in life. I’m 30. Lots of my much younger catholic friends have been married years now. He’s not too young to have a previous wife who passed on. Would you consider him if all his partners had been his wives, who later died? Weird scenario, but it puts things in perspective. If he’s willing to wait with you, that’s important, the rest counts for little.
I’d spend some time thinking about the person you want to become in the future as well. We’re all called to be saints. At 28, hopefully your faith will still grow significantly, and a husband should empower that, not be a compromise to it.
Sure he’s fine with Sunday mass, but if you think there’s even a chance you’ll want to go daily in the future, will he support that? What if you want mandatory family prayer time with the kids as you teach them the faith? Will he support that, even if it means dealing with a child who might prefer to play or watch tv? Will he help you stand your ground, despite it not being his faith, or will he try to get you to back down so the child stops arguing? Speaking of children, have you thought about the reality of raising the kids catholic with an agnostic parent? Lots of folks say they’re willing to but don’t think about what that life will really be like. Sunday mass, meat abstinence on Fridays of Lent, Easter and Christmas being firstly about Christ (and not Santa/Bunnies), concerns over the curriculum in schools, appropriate vs inappropriate tv… etc. I could go on. It seems like a lot of little things but don’t the little things make up life?
Sorry if the above makes it seem like I’m pushing you to end the relationship. Maybe he’s okay with all this. If so, great! But you both need to be very clear about where you really want to go in the future, and what you can expect from each other. At your ages, you should be prepared that he will continue being agnostic (and maybe become more so), and he needs to be prepared for you to remain catholic (hopefully growing in that.
Start having these serious conversations!