You do need to be aware that there is the possibility that your credit rating may be affected, if he is giving your address for his letters etc. The debt people can look at the address, and not necessarily be aware that you are not involved in his financial situation especially as you are his parents.
You should make it clear , that now he is an adult that you are no longer responsible for his debts , and will not be responsible for any of his debts, I expect you are not charging him a fair rate for staying with you, even for the cost of food etc. . When my son had a patch of problems I agreed to him coming home to live for a time, but told him the amount I expected from him weekly for his keep etc. Of course I did not charge him the full amount, but did make it clear that he must pay his way. In actual fact I kept most of it apart from food costs, in a savings account. When things had improved and he was getting back on his feet, and moving to his own place, we were then able to give him a lump sum towards some furnishings. He was surprised and very pleased .
At another time he asked to borrow some money, for quite a sensible thing that was on offer for a short time. I told him that we only had limited money and that if we lent him the cash he must pay us back as quickly as possible as this was the only cushion we had for any unexpected costs. Also should he ever need to borrow money again, it would only be there if he paid it back in the first place.
This, in the end, was a good lesson for him to learn, which he did and now much older, he has his own emergency funds for the unexpected problems that arrive. He has not needed to borrow from us for many years , and I saw that as a way to teach him our way of surviving, without actually saying that he had to do this.
You will not really be doing your son any favour if you let him think that you will provide, home , money etc , and keep him from facing up to his own way of living. He is an adult now and should expect to behave like an adult. In fact once he has gone somewhere of his own, I would suggest that you turn the bedroom into a working room for sewing or office or whatever, so that you are tacitly showing that you do not expect him to return on a lengthy time scale and that you have done your share and more and he must not rely on you to do anything. By now HE should be providing support and help for you not the other way around!!.
We have all struggled to bring up our families and manage to get a home together. Today it seems that we are seen as being there just for their convience to look after children, whenever it suits them and to bale them out of whatever stupid situation they get themselves into. Well you should be able to enjoy your time and not be involved in all this worry.
Do think about these ideas, and maybe come up with something more suitable to do. Do you have any other children who are not behaving in this way? This could end up with other family members resenting the fact that they have behaved in a better way and yet he is getting much more of the money than he should. It sounds very selfish to me and I think you should give more attention to your husband, and friends and let him make an effort for himself