Looking through some old threads for you and doing a bit of research. I gleaned this information:
The engine defiantly needs to be warm for the compression check. Also make sure the throttle is wide open too.
Make sure your valve lash is correct. I read in the older thread that having the valves adjusted too tightly will cause a drop in power, but what is the effect of having the adjustments too loose? My intake valve lash is between .007-.008 on all of the valves, will this decrease power as well? I know that back in our bando days guys would set the valve lash tighter for longer tracks to gain top end power and wider for shorter tracks for low end power.
Yes, cylinders should all be within 10% of each other.
I will do some other searching and see if I can find anything else for you.
Welcome to the site!
Steve