I would say he's okay. I know what it's like to have a tank get way hotter than it should be. I live in West Texas and it's been in the nineties recently. My poor AC can barely keep up some days, typically between 12 PM and 2 PM since those are the hottest parts of the days and it just craps out. This causes the hot side of Calliope's tank to spike up to 100-103. Of course I instantly turn off her heat sources and take her out but it hasn't caused any long term damage to her so far. It doesn't look like he has any burns on his belly so he should be okay.
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