Army brat, ex wife & ex mod admin here.
He's spun you a load of bollocks to be honest!
What rank and trade is he in? Would enable us to check his pay, you to check his pay actually or do you already know what he earns? Ah you do know what he earns and he's feeding you bullshit!
Also he can use his work address for mail if he's in barracks Accom so bullshit he needs to use your address.
Get onto cms ASAP and get a claim in.
Contact your local welfare advice office and get their help to re-establish your claim with tax credits which you are entitled to
Tell him to stop using your address!
If he gives you any grief on anything contact his CO and tell them the problems you're having with him. They're not necessarily helpful with cm in my experience - though others have had better experiences, but messing you up with the mail nonsense they will sort.
"I would be far better off single" you ARE single in any way that makes any meaningful difference to you or your kids. Your youngest already doesn't have dad there all the time and is part of a "broken" family because quite honestly it was never "whole"
You are being very naive and irresponsible not to recognise and accept that
"I wouldnt want to kove into military housing no, that would mean uprouting my children every few years." Then frankly you shouldn't have got together with someone in the army! What are you thinking will happen when he next gets posted? Which could include overseas?
"He cant get travel costs because henhas the accomodation, so they see he has no need to travel back" also bullshit! That's not how it works at all!
Cut this abusive tosser off, Claim tax credits as a Lp, claim cm and stop being such a mug!