So very stuck...

Yes, you can be getting detonation. Octane boosters are, well, I'll try not to be too mean but I think it's safe to assume you're not actually getting a +7 octane rating boost, if any at all.

The 340 in my Duster has a cranking PSI around 180 as well, I had to pull some timing to keep it happy under heavy load. I also run the 308 swirl port heads with 2.02"/1.60" valves, they've been ported and the chambers worked some. Cranking PSI can vary quite a bit on how you're doing your compression test, so it's not the most reliable thing to compare. My static compression is 9.8:1, also with KB hyper pistons.

Not sure what your timing is set at, but that will make a BIG difference. I'm at 20° at idle and 34° all in mechanical.

You also have a heavy vehicle, with a lot of rotating mass, and 4.10's aren't that crazy for 35's. I'm no tuning guru by any means, but if it's coming from the engine it could definitely be detonation. And those hyper pistons do not like detonation, so you want to figure it out.