does not include shipping and tax
will this work on my Benjamin Discovery, is there a regulator down to 2000 psi
You need part number PY-A-4926 to make it fit to a disco. No, you just need to keep an eye on the disco's gauge.
How do I attach my Hatsan AT44PA fill probe?
It threads on to it directly.
Will allow you to hook up a male foster quick disconnect.
will I need an adapter for the scuba tank assembly to fill the maurader
Yes you will need "PY-A-4926" (type that into the search bar). That will thread into the end of the hose and connect to the quick disconnect fitting on the marauder.