It certainly looks like you have covered the usual suspects
Just to go over I assume Somewhere it got a new spark plug
Does seem heat related as it comes up after its warmed up.
Did you look at the jet sizes, even though it sounds as running lean
Another heat possibility is a weak coil or spark plug boot/cap and wire.
If the carb bowl floats have been slightly bent they can rub against the bowl
sides and lean her out then free itself and back happy
But first always
SEAFOAM IT no I am not kidding