Alright! So did that test per stick and everything went fine, but here's something *really* interesting.
Another guy who's helping me troubleshoot on the Tech Support subReddit suggested that I disable Hyper Threading and see if I had any issues then.
disabled it in the BIOS, and I've been running Prime95 Blend test for over an hour and a half no prob! CPU temp is sitting around 70-72C.
What do you make of that?