Re: WWYD... overweight friend and new furniture...
Wait a second. Your friend knows he's heavy. Just tell him he's been breaking your chairs and he has to sit in the metal fold up one or whatever. We had a very heavy friend who we used to game with and we had a rolling desk chair that worked for him.
The fact that he's heavy is obvious. Just deal with it honestly. Why beat around the bush or wince when he sits down? Work with him to find a solution.
I run the Frontier Wholesale co-op in February, May, August & November