5K Engine Compresion

[Damomate]

i am a learning home mechanic, i have a toyota liteace with a 5k engine, i buggered me exhaust valve and was running on three cylinder for about five months, when i finally learned enough to fix it i took the head off and it was cracking ( no surprises there) so i just did a head replacement & my new head has been shaved back quite alot. the rods were too long & to compensate i jacked up the rockers with spacers and made a little plate with a hole in it for the oil vein, i have found that i cannot set the timing with a timing gun as i get pre ignition so i have retarded it a little, i have also found that higher octane fuel has helped alot and am getting alot of extra kms per tank, i just did a compression test today and the reading was 200 psi. seems to be running quite well now.

my main question is what is an acceptable compression, is 200 psi too high?

if it is should i consider a second gasket to increase the CC?

any other tips for tuning the engine or increasing my fuel economy?

what do you think about the rockers being spaced up?