I was going to say just give in, it is cheaper than therapy, but FOUR in a year? Yikes.
How about one of those foam folding things? No wood construction that can snap. I saw quite a few options when I searched "foam sofa." OK, this isn't going to be high style, but I'm sure you are more than ready to give up style, and just have a place to sit.
I went to a brown leather sofa as my version of "indestructible," but apparently my force of nature has never been quite as destructive as yours.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).