Proton is actually a very good EC board. The radius is 13m (just like the Swoard 168) and it should flex softish at your weight, which is good for EC. You should be able to make it turn very tight or let her cruise longer turns. I do not see why it would "go straight down the fall line"… EC is mostly technique, as well as the speed of the ride.
Oh, btw, the Protons have a metal/titanal layer in them. It's the "wings" that you see in the top sheet.
I have both a Coiler All Mountain 172, a Coiler Pure Race 186, a Coiler VSR 176, and 3 Oxygen Protons (164, 168, 172).
I find the Protons very easy to carve with good technique, forgiving on variable snow, and especially good on ice, considering that their titanal wing technology was around 10-15 years before the advent of full titanal boards. I get between 25-55 days a season on these boards, and rotate them depending on where I am riding and the snow conditions.
My first board was a Proton, and I found that it did not like tracking across the fall line as much as down it. I'm sure most of that was technique, but after hopping on other boards that's what I remember about it.
Personally I always preferred carving on the Whaka side, but Turoa is probably a little better and easier for improving on. There is not much replacement for time on the mountain, and the Oxy 164 provided it isn't completely knackered should do you fine; they have not much taper in them (difference between the nose width and the tail width) so from what I can recall riding on them, they were quite easy to hook into a turn and carve right out the other side of the fall line, certainly more likely to want to hold the edge than my more modern sigi grabner, which is very happy to let go of an edge when you want (it's actually a good thing) as you pivot or modify turn shapes.
Oxygen – The Proton has a tail that sticks like glue to the snow. It has a notch centered in the tail edge, which screams "alpine board!" Oxygen's parent, Atomic Ski, may or may not continue the Oxygen line.