The Hayden "Oil Fix" corrects base-gasket leaks, so I doubt if it'll repair the OP's problems with blow-by.

 

The Evo is a very dependable motor when set up properly, but the oil barfing is something you might need to get used to. My '96 RK barfed, although not much as you're describing, and so does my '07 SG. In the latter case I installed the Fuel Moto modded SE AC that channels the breather oil into the velocity stack, and thus gets sucked into the intake never to barf through the filter element again. I would call Jamie at Fuel Moto and ask if a version is available for your bike, although he doesn't list it on his website.

The Evo uses no oil pressure in a conventional sense except for the lifters, and your pressure sounds close, although it depends on the accuracy of your gauge. Hot pressure of 20# is about right, and you could see zero on a gauge at idle when hot, although it isn't really zero if the lifters stay quiet. Your OP light should not be coming on, however, but if it flickers at idle when very hot I wouldn't worry too much as long as it picks up above idle and you hear no lifter clatter. If the lifters are not clattering you have enough pressure.