So a couple of things here to help?
Sounds like your hubby is afraid of your son not making it again and reacting negatively. This is very emotive for a lot of men.
My son plays for a cat 1 and internationally so like other I may be able to help a little bit?
First development teams are about making money attached to the club. They aren’t about moving kids from development to academy. Sorry that may not be nice to hear but it’s true.
Almost no one goes from development to academy. Training once a week and games once a week isn’t a true reflection of academy life which is four times training a week and game on the weekend. The gap is too big and if your son wants it he will have to train at least twice elsewhere to be able to keep up if the opportunity for a trial comes up agan.
A lot of kids mature later and it really depends on what position your son plays so I wouldn’t worry about his size/weight at this stage. Some of thr best players come in around your sons age and it may interest your husband to know that onky abiut a third of my sons team have been there from day 1. Most were 13/14/15 when they came in.
If you son wants to make it he will need to excel completely in the development squad and if very lucky will be offered another trial. In all our years we have known one kid to do that and be successful. One. I say this to be realistic.
A cat 2 if very successful is probably looking at a league two career probs if lucky. That’s a good living and a good life but almost certainly won’t be PL or Championship. It depends on what ‘making it’ looks like. Being a pro can mean very different things.
I would always support my children and it’s worth understanding why your husband feels this way. The commitment is big if your son is successful and like most other kids there will be big bumps in the road (injuries, releases, scholar decisions etc) so your husband has to be onboard with that.
Good luck.