It's good that you're thinking about plan B IF he doesn't get his settlement visa in the future, but remember its a little more cut and dried now as far as the regulations on earnings are concerned, so if you earn over £18,600 AND you can prove the rest, ie genuine relationship etc, which I'm sure you can, then there's a very strong case for it to be granted.
As far as your current situation, everything you can throw at them for sure will help....no it's not ideal to have to just drop everything every month and go!! But unfortunately it's what a lot of us did have to do if we wanted to be with them. You are absolutely doing the right and sensible thing in trying to get him a VV first so that he can get to know your family and you've got some serious time together before you commit to marriage. Shame really the UKBA can't see that....
Is there no way his employers can write to say that he will be recommending work when he gets back? Does he rent anywhere there that has a rental agreement or something?
No he doesn't rent as he's still at the family home and no one is willing to help him. Would a letter from his father explaining his grandmother's ill health and the fact he cares for her help do you think?