Ye he's miserable in the army so it's a big con to try and stay there. But everything else seems to have lots of cons too lol.
If he has children then there’s no reason why he can’t get a house and no reason for you not to be able to live with him. I am serving and my partner is civi. We are not married but have a daughter and a baby on the way. We all live together in military housing. I’m happy for you to message me directly and I can look into this for you!
If he leaves the army, you're not entitled to anything. Also kids entitle you not to anything either. If you can prove a LTR they give u surplus housing if available, but there's no guarantees for it
I am not married to my partner and we have a child and live in military housing, the only proof you need is that you've been together at least a year (shared names on bills/join account) or a birth certificate, we had to wait for our sons birth certificate as we had no other proof. Im not sure how it works if he's leaving and how long you'll have before you have to move out
In my experience no you’d have to be married I have children with my partner and when my second was on the way we applied for housing (also engaged getting married next month) they turned us down so partner handed in his notice, once he did that though they finally agreed to move him up north and offered him every course he’d previously been turned down from before his promotion, he’s just finished working his notice and is now up north with me again