As for "breathable". Just leave a few "holes" in the plastic fabric. In areas he cannot reach to rub on. If you have a light dome, you can also cut out a circle for that, unless that is where he rubs..

They really do not need a whole lot of air flow, unless you keep the enclosure very humid. As a matter of fact, it should help you keep some of the humidity from escaping If you worry about it, just lift it a couple times the day...

And good luck with everything, your boy sure is one handsome snake !! Post more pictures when you get a chance