what do you do about living next to someone who is so aggro
Either keep your head down and move asap or stand up and fight.
If you do the latter them you have to go for the win and get as many neighbours behind you as you can – all of whom are willing to report issues.
My sister was a Police Inspector, her husband a retired one and it nearly broke them dealing with nuisance neighbours so don;t start unless you’re prepared to see it through.
tbh, violence (or witnessed/recorded) threats of violence probably play into your hands as the police can be involved rather than just the council.
If the son has a public profile you could try and play on that ‘you don;t want to end up in court – it’ll affect your sons career’?