Did you clear out the whole accountand leave nothing in there? If you did then despite how angry you feel at him, I’d return his half minus the cost of what it entailed to break the lease. Id also charge him on top of that for the time it took you to sort out and pack up his half of the life that he left you to do when he refused to do when all this went down.
So if he is legally required to recieve 5k back from your account then minus every minute and hour that it took you to sort out his half in this. He left you to be his personal assistant in all this to sort out his life. A junior personal assistant in Australia for example gets paid 55k a year plus 9 percent superannuation on that. They are paid to work 37.5 hours a week. If you did the math it would cost their employer $55,000 plus $4500 in super contributions to hire them per year. If you break that down further it would cost an employer $1152 per week to employ them or $30.75 per hour. I would do the maths as to what a P.A earns per hour in your country/state and charge him accordingly for the amount of hours it took you to be his PA and sort out his life and his share during the moving process. I’d include
1. all your emails, call logs to your landlord
2. All your correspondence to him asking what he wanted to do including phone logs, sms, email
3. all electronic evidence of how much time you took trying to get rid of his belongings he left behind for you to get rid of with his permission
4. the time it took you to do the typical end of lease deep clean of an apartment
5. All the associated cost like packing boxes, cleaning products
6. The electricity used during cleaning, like light use, vaccuming etc.
I’d go as detailed as possible and break everything down as minutely as possible with evidence and use the PA rate of pay per hour. I’d ignore him until you figure all that out and then I’d send him a big long itemized bill via email with all the evidence and break down costs.
Eg 5000k of his half of the account
Plus x amount $ for his half of the security deposit return
Minus the cost of materials used in the moving process (cleaning, electricity, moving boxes etc)
Minus all billable time it took you as his PA to sort out his life in regards to him shirking his responsibilities in sorting out the end of lesse requirements.
Id then tell him he will get back x amount based on your calculations above.
If you do the above with method, irrefutable detail and fairness, he won’t have a legal leg to stand on if he decides to try and take you on in a legal setting for his half. This is the best way of getting your own back and doing it in a legal way. He should get half of your joint account but he should also pay for your valuable commodity of the time it took you to sort out his half of the mess he refused to deal with in the wake of his shitty choices.