low compression/wide cam problem

I have long deck 302 block, and I need to gain some compression to wake up this engine. Wondering about milling those .030". Wondering how far is it possible to go? Can I have piston at TDC above the block let's say 0.01" with regular gasket 0.04" thick?

The engine has some 8.78:1 (218/228 cam) making only 130 cranking psi.
What pressures are safe to use pump gas with cast iron heads?

I would like to avoid replacing pistons due to their cost. What I see on every corner are expensive performance forged pistons prized $500+ while regular cast dish pistons cost 80-100 US/set. Yet are there any OE domed pistons fitting sbf? Looking for -6cc maybe -8cc.

d2OE heads (58.2cc). the cam timing is measured at .050" lift, otherwise it is 280/290. So I should rather play with valve timing instead of milling the deck/head?

so: intake opens right at TDC, exhaust closes 5°ATDC, measured at .050". Would that make sense to advance intake opening to e.g. 3° BTDC and leave only 2° for exhaust ATDC?

Advancing by 3 degrees would make exhaust valve open at 56° BBDC instead of 53° BBDC. Would that have any negative impact on performance?