I'm quite confused about the priorities of you and your DH as parents.
On the one hand, you seem quite happy for your ds to avoid getting a proper job or having any adult responsibilities in favour of having more time for his hobbies or a lifestyle experience like Mark Warner, and the the reason that you give for this is your perception that these things will look good on his CV in the future.
On the other hand, your DH seems keen to persuade him to forget about some universities that really would look good on hid CV in favour of going somewhere like Wolverhampton??!
The mind boggles! I honestly can't quite figure out if you and his dad are really at odds about what your ds should do, with you only being concerned about his CV and not caring about the cost and his dad being completely the opposite. Or whether you are both just completely clueless about what would really look good on a cv and are both therefore advising your ds quite badly. Or something else entirely??
Getting a degree from a good university will really help your ds, especially with a non-vocational subject like history. While the police/army might not care where he studies, he might well change his mind about going down these paths at some point, so it's best to keep his options open.
Aside from that, sport and other extracurricular activities are all great but won't make a massive difference to your ds's employability, but work experience will. It doesn't have to be glamorous, high flying work experience. There is value in proving that you can stick at the boring, menial tasks as well. As he is a good swimmer, lifeguarding would be an excellent option - one of my dd's friends does this and I believe the pay is pretty decent.
DS is not being unreasonable to want to go to a good university if his grades are up to it, and you and your DH shouldn't discourage him from this - he may always resent you got it if he feels that you pushed him towards an option that is below what he is capable of. That said, he needs to understand the financial implications of each choice and to accept that he will need to contribute to his living costs if he chooses one of the more costly options.