Hi,
This is something only you, your fiance and your son can decide upon once you all sit down and discuss things.
From your post, is it your son who's in an apprenticeship ?
I assume your fiance is the one who doesn't meet the financial requirement?
Moving on, take a look at your current earnings, your son's future potential earnings etc and then take a look at the UK and then perhaps the Manchester area as well. What does your fiance do? what's his earning level and future potential level?
In every sector, the UK pays less than the same sector in the US. Cost of living is lower in the USA, standard of living is higher in the US. These are of course high level economic indicators but based on actual data and statistics.
I'd suggest overall that you perhaps look to marrying your fiance and have him move with you to the USA based purely on financial aspects, after all, its money which makes the world go around and from that, you can assess your own personal situation. Yes, there's plenty of American's who moved over here successfully and prefer the 'atmosphere' in the UK. There's similarly plenty who 'thought' they'd love it and moved over with companies and via personal marriages etc, who relatively quickly went straight back to the USA (I used to work with many people like this!) To be balanced, I know people who went to the USA and quickly came back here as well as those who went to the USA and never looked back!
I agree with the above as well, moving to the UK doesn't automatically mean a 'better education' for sure. That will depend on the quality of the school and the teachers.
Once you all sit down and discuss things, take into account legal requirements and aspects you need to know perhaps from an immigration lawyer, you'll be in a better position to discuss as a family what will be the best thing to do.
Good luck!
Cheers, DtM! West London & Slough UK!