Kerry,
Sorry I didn't reply to your email, we had a big exercise last week and I was running hard.
There are a couple issues I see.
First you need to figure out how to drop that gasket a little lower. It lines up with the port now, but the gasket is high everywhere else, maybe try a different brand of gasket and see if it sits a better on the port or drop the gasket and trim the roof.
Second, I'd consider shaping that hole a little to make sure you have good drainback, just blend it a little so you know it'll flow and won't give a place for any gunk to build up
Third, sealing the oil drainback is simply a matter of making sure that outer wall is sealed by a gasket, and the gasket has good crush. Once the gasket is sitting in the right place you can figure out if the gasket will seal.
I would be VERY mindful of where the RTV flows with that setup, if any pushes into the drain, it'll plug. All the more reason to shape that hole for a nice clean return.
On heads/intakes that need some fitting of a gasket like that, don't be afraid to do what you need to do, including cutting off the locator tabs on the bottom. Just remember, if you do that, glue the gasket to the head so it wont move.