I would do a spreadsheet to show your h what comes in and what goes out in the way of money/bills. You will need to also factor in a bit of "rainy day" funds for emergencies that can and will crop up during a month.
You don't tell him to move downstairs. You suggest it and let him mull it over. It has to be his decision. Telling him to do so makes you sound like his mother. They are more receptive to suggestions that "telling". Also, I wouldn't put a time limit on re-evaluating the situation. Why? Because he will be counting the days to the 30th and this will come up again. I suggest that you state that "if he does decide to move downstairs, he can always re-evaluate the living arrangements at a later date and discuss them w/you". You have to put this all in his court. You aren't his mother and you can't control what he does.
BTW, if he is h@ll bent on moving, he will find a way to do it, money or not. There's nothing you can do to stop him from moving out. Whether it's a dump or not...he will make the decision as to whether he wants to live there. As for your children, if it is a dump, then you can advise him that it would be better to visit w/them elsewhere due to safety and environmental concerns...but you are jumping too far ahead. Let's see how it plays out this evening.
Remember, you need to give him things to think about and make decisions himself. Also, speak to him as a business associate and do not tell him what to do....you aren't his mother, even though he acts like a spoiled brat at times.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
