I've seen countless similar situations and the cold feet was not just limited to men (majority though, tayong mga lalake).
IMHO, it is basically the sudden realization that marraige involves certain responsibilities. You can count yourself lucky that he was suddenly courageous enough to acknowledge that he could not perform these responsibilities.
Mind you, these responsibilities are not just financial. To include another person in your life means numerous compromises to your quality of life that you never had to make or consider before. As a trivial example, the ubiquitous leaving the toilet seat down. Of course, ako palaging "Yes darling..." The compromises increase even more when you have children.
That's what true love is, the desire to give a better life to someone else...the question in your situation now is, is he willing to do all that is required to give that to you? A trivial example from my life: I give up clubbing every night (weekends nalang), minsan nalang she does her highly therapeutic shopping (nakow, naatake ako noong bf/gf lang kami sa mga gastos nya, even if its her own money)
I guess you just have to find out what certain responsibilities your man is afraid of. This is no easy task as this isn't something you ask straight out. This is more of something you discover through observation... what are his pet peeves, what he doesn't like about his parents, what are things he absolutely must have, what thing do you not have in common, etc. (Not to discourage you, but I have a friend who absolutely could not give up other women, fafable kasi sya e)
Related to your finding out is, have you both discussed what either of your general responsibilities would be in marraige? I believe ayos na ayos kami ni misis cuz we set up some strict general guidelines before we got married. For example: I know of 1 couple in the US where naging houseband si hubby kasi their agreement was breadwinner yung kung sinong mas mataas ang sweldo.
Yung problema lang e, he wants space...hmm. If I were you, try finding and talking it out as mentioned above. But if he really wants his space, I wouldn't dwell on it na... kung ayaw nya e di wag. Hard to do, but not impossible. If he wants space, give it not just to him but yourself as well.
It is my experience also na pag sabi ng guy na "I love you but I need some space..." e it really means "You know, you're still hot but..."