Alright, well I've been involved in 2 serious relationships and with both of them I've had most of what you listed.
With the first, I was still pretty young, after 5 years of dating I don't think I knew myself well enough to know if she knew me better than anyone else or not. Otherwise I'd say that I had all of those things in my first relationship.
With the second, I was much more mature and can say that after a couple of years I really did have everything you listed.
As for living with someone... Other than a persons own reservations, I don't really see any reason that you can't spend all of your free time with someone outside of marriage. Certainly spending the night in bed together isn't a valid option, but I don't think that's what you were referring to in the first place.
As for the OPs question... I'd say the only real difference between a serious relationship and a marriage is the vow. Assuming both parties take their vow seriously, you end up with someone that you know will be there through thick and thin. That vow makes a lot of things that Juli mentioned a lot easier. However marriage certainly doesn't guarantee those things. Likewise, I've seen that the trust required to achieve those can be achieved outside of marriage. Which leaves the only guaranteed difference still only being sex.