Welp, I figured out my problem! /facepalm. Was changing the wires and plugs, all the plugs were looking really good so I was just going to leave them. Then I get to 6 and 7 which are COMPLETELY fouled, but the rest look fine. So I double check the firing order (which I haven't touched since I bought it a month ago) and sure enough, 6 and 7 are reversed on the cap. So I flip them, finish the wires and fire it up. Even with the old cap, rotor and coil still on, warm idle had immediately jumped to 1200 rpm (had it set at 850). So I turn it back down to about 850-900 and let the water temp come up. Before even in neutral I couldn't get it to rev past 4200ish, was almost like the distributor had a built in cutoff for a redline, which I didn't think it would, not that low especially. Now it free revs to 5,000 just fine!
I'm shocked how well it ran before. It wasn't really misfiring and it didn't sound like it wasn't running on all 8. I had Jeff from the forums over and even he agreed it didn't sound that off.
So after fixing that and replacing the fouled plugs I can't wait to see how she runs out on Monday! Hopefully I see 45+ and more RPM with the prop I have, and now I have a better baseline to mess around with different props. Woohoo!