Deposit from a subleased room

Hello everyone
I have a question regarding a deposit that an old roommate of mine is waiting to get back. Long post, sorry

I am a young person renting a newly built apartment.
I acquired the contract from a previous group of friends with which I used to share the apartment (and the contract) with. They all moved out, and because it’s so hard to find anything affordable, I decided to stay and rent out the other rooms.
One of my ‘subtenants’ just moved out. He physically moved out at the end of June, but officially his lease ended on July 31st (relevant later).
We had a bunch of people moving in and out, as it often goes. Our past few roommates left a small part (around 2k) of their deposit (that was up to 22k) for regular wear and tear of the place, and to fix any damages done in the rooms. It wasn’t specified in their contracts, which just stated that they (as tenants) were responsible for up-keeping the rented spaces (ex: painting, whitewashing, filling of holes, cleaning, etc). The previous roommates did not do any of these things, therefore left the money. We just agreed on an amount together.

Now, we have talked about this with this particular roommate when he moved in. He states that we talked about 500/1000kr max, i disagree, as I clearly remember saying that it depended on the damage/length of their stay. But its his word against mine, so i know it doesn’t really matter.
When he moved in, his room was freshly painted.
He had drilled holes in the wall, and attempted to fix them without success, so I will have to fix it again, buying materials etc.
I also had to clean his part of the fridge and throw out all the food he had left when he moved out, because he didn’t. I have this over text. To me, this is not living up to the responsibilities stated in the contract. He had a whole month to do all of this, but left it for the last day possible. He also forgot to leave the key, so i had to go and pick it up somewhere he left it at, which was very inconvenient for me.
Moreover, during his whole lease, he has been late with payments of all the bills. I had to send him reminders every time, multiple times. Sometimes had to wait for months to receive his part of electricity bills that accumulated. It is specifically stated in the contract that the bills need to be paid by the last bank day of the month. I did not terminate his lease early and I have been very patient (even though i have voiced my frustration many times) because we are friends, which is why this situation is particularly upsetting.

He has lived here for a year, so I suggested an amount of 2k that he declined, and he is firm on paying 1000kr, and won’t budge because the amount is not stated in the contract. Fine. It’s not about 1000kr. For me, its about the principle regarding of all the above, which is a breach of the contract. I am asking for advice, because I have decided to agree on the 1000kr from his deposit for wear and tear, but I am considering charging him small fees for all of the other situations, attaching all the written proof. I am just not sure how this works and I’m hoping that anyone has any kind of advice for me. Before anyone comes at me thinking I’m a crazy landlord trying to rip off people, the deposit for the whole apartment is 80k, so a total of 6k left from all my previous roommates won’t change much anyways. It was all done in solidarity amongst roommates that had good relationships with each other, and knew about the financial burdens for young people living in Copenhagen.