My ex has always been a thin guy too. He works out, lifts weights, but he has a small frame. He's about 5'7'. He was sually somewhere around 165-170lbs. Well, I will never forget when he was dropping the bomb on me, he wouldn't come out and say it and I thought he was telling me had cancer because he had gotten so thin. He was down to 153lbs. Well, I realized later it was probably a mix of guilt, depression and anxiety due to his affair.
Your ex is probably not doing drugs but is probably pretty depressed. And lonely. Which is why he making his home an AirBNB. To have people around.
Hopefully your kids can talk to him telling him that they feel uncomfortable in this situation.
