Bad smell from flatmate's room

Hi OP

Would you feel comfortable ask him if he would like a helping hand in cleaning his room? As in pull beds and wardrobe from the walls and use a carpet cleaner? Find out if there's any mold on the window or walls and try and attack those with a mold spray?

He sounds very reasonable and is doing all he can to help keep his roomates happy. I'm not sure what else you expect from him. I would understand if he wasn't complying and was ignoring every word and action you've used but the chap sounds like he's doing all he can. If the smell isn't from him himself or what he does or doesn't use, it mostly likely be from a surface in his room that hasn't been tackled.

If it's a musty and damp smell, I would imagine that he's drying his clothes in his room gathering the damp smell which is a given. Maybe suggest drying his clothes in the sitting room or even outdoor balcony if you have one? Just until the air goes out.

I'm not sure what else you can do. I would suggest moving out if you want to be extreme but to be fair to your roommate, I'm sure he's a lost to what to do considering you've named the hygienic things he does