to sum up:

new job = more £, support of mrs but you are having doubts

old job = less money, boss being a cock, boss giving you shit before yuo've even got back

i fail to see where the problem with the new job is mate

as others have said, it may take a whle to get into the swing of things and i know it's been hard for me to be without the mrs and son for the past 2 months or so, but, if i were in your situation, i would be exptremly tempted to take the money while i could, at least you won't be stuck in a job that you don't like not earning the money you should be getting just ebcause you feel "obliged" to help out your old boss
on the other hand, i also believe in not burning your bridges, so if you can explain to someone else that you won't be back until you have finfished whatever contract you are going to be on it gives you a bit of an exit strategy for when you might get to the position where you miss yourfamily too much