Custom mechanical fan builder

Three things I would do BEFORE giving up on the current set up

1) flush the cooling system until clear. Might mean running thru several heat cycles. If whatever is in there is not completely out, we are chasing our tails.
I think it is residual product left from the original casting of the block that somehow got trapped and is gradually braking free and gumming up the radiator / thermostat opening.....but that is just my guess

2) install a 160 stat ( verify before installing) with a bleed hole

3) add a product called Water Wetter with new coolant mixture once it is completely flushed. I used it before. Claims it keeps temps lower and more consistent. Worked well in my first Hemi Duster with non aluminum radiator.