Wow, clearly in the minority but I don't see it as him future faking @Toolittletoolatehmm - ultimately didn't you both decide to not blend your kids homes? It's fine that you've changed your mind and fine that this set up is no longer working for you, but it sounds as if he is keeping to the plan of moving in together and moving forward with shared lives once the kids are older. Again, fine if you don't want to get married, but that's a huge thing he was planning and surely a very clear indicator that he's fully committed.
Other than separate houses, do you feel like you're in a partnership? Is it a 'living apart together/LAT' situation? It's still ok (of course!) if it's not what you want - it's bloody hard running x2 homes, bills, kid stuff, practical stuff, other social stuff AROUND a relationship, but there are merits to it too, so long as the thinking behind it is genuine, and there's an end in sight.
I'm only 3 years into my 'LAT' style relationship, so I don't realistically know if we'll last 10 years living this way, as much as the relationship is brilliant, as you're right it can be hard and lonely. Although I do enjoy going into full goblin mode without him at times, and so rarely having to compromise... Our kids are younger, and it wouldn't be practical for them to share a home - same city but 30 minutes apart so either long daily commute and living away from friends, or moving school/losing friends.
I read so much on Mumsnet about the difficulties of blending families and how it's never the right thing for the kids, yet your OH (and you) are doing this and he's getting slammed every which way. What I picked up from your posts, though, is that he's lovely, fun, cares about your kids - and that you've been really happy together?
Obviously if he's been treating you like a casual girlfriend for several years that's different. But if you both agreed this, and if you holiday together and show each other commitment in other ways I think that's different.
Your post about one bed to make, someone to decompress with on an evening, taking it in turns making dinner etc. really struck a chord though. You're not in any way wrong to have had enough of living apart. I just urge you not to get pulled along by the MN army who mostly can't empathise with your situation, and are largely taking issue with his possibly clumsy but sweet chat with your parents about proposing.
Hope you can have a proper think, talk with friends, talk with him etc. and work out what's best for you. Good luck 