I had calculated March 30, 1966; oddly enough that is my X wife's birthday too. A wise man once said, "If it has tits or wheels it will give you trouble."
I agree it looks like a flanged nut. Not the right one. If it is pulkl the washer out and you should be fine. But you may be better off just getting the right nut.
Dyno
Almost NEVER need to replace, remove and clean as well as replace grommet. Grommet will be as hard as a rock be careful not to drop pieces into the engine. Soak old PCV in solvent and continue to use. If it is OEM it is a quality piece.
Dyno
It is flat glass, maybe someone with the glass out can make a template and post it. most old school auto glass shops can cut one out based on a template. I have had this done with 40 series windshields.
You most likely will have to disassemble the ABV. As the vanes in the pump fail the debris get loaded up in the ABV. Be careful not to mess up the screw heads, use a JIS impact driver to break them free. There are NO rebuild kits or gaskets available for it.