I think you are going to have a very difficult time convincing CL that you are not in a relationship, TBH. Him moving back in for financial reasons is going to be seen as financial codependency. The fact you are in the same bedroom will also be a hindrance.
It is REALLY hard. There's a lot of paperwork, and regular checks. You need to provide proof upon proof upon proof, and then some more, that the relationship is over. The fact that it's your parents house, so he'll essentially be living with his ex-in-laws makes it complex too. Get your hands on the forms, or call and have someone talk you through it. DH and I went through it all in 2011, only to decide that it would be easier to physically separate, which we did.