AW, it's tough competing with a mistress - especially one that plays as dirty as aviation.
3500 hours is ok. The problem is obviously his multi for most of the regionals, RFDS etc.
Has he applied to QF and other airlines? QF looks for 500 PIC with no multi requiremet. Cathay wants 1000 hours with preference for multi. There are jobs out there for multi - he's just got to find them. However, that's not easy with a young family (?) particularly if you have to look at moving from major capital cities and family support.
Some employers may prefer an older pilot with a family because they're less likely to move on as they know of the ties that bind someone with a young family.
Someone has already suggested getting a ME Training Approval and trying to increase his multi hours that way.
In short, you're up against it with his age/experience profile but it's not out of the question. It fundamentally comes own to his attitude and how far you're willing to go to support his dream. If he hates instrucing and isn't willing to move for multi, it makes things harder.
I wish you well and hope you make a decision that benefits you both.