I want non FL wiih Pyrex tank and clamps, old threads were easier to handel.

That sounds like a genuine Dvarw...
for 100$+ more.
Well I clamped one of my old dvarws. But clamps were taken out of the Pelso's box.

And prefer the threads on the old ones too.

As for the chimney cap, it's a question of o-ring. And some lubrication might help where you don't want to be stuck.