I would think you would have better idle and vacuume if the lifters were not pumping up. Less durration and lift.
Its been years but I seem to recall running my engine with the valve covers off and getting oil all over the place. Then again I may have been doing this during a cam break in with a lot of RPMs.
Do you have a priming tool for the oil pump? When I do a new start up or if its been a long time between startups I typicly will prime the pump. With the valve covers off I look to make sure I get oil comming out of each pushrood. I usally have to turn the engine a 1/4 turn at a time to get them all working.
I would think you would want 10 to 15 deg initial and with the vacuum can another 15 to 20 deg so 30-40 deg timing doesn't sound that bad with vacuum adv connected. I assume you are measuring timming correctly with the vacuum can pluged and disconnected? With the 112 deg lobes and the small durration you should have a nice smooth idle and good vacuum for sure.
Have you re tried your compression test since adjusting the valves. I agree that your test should be higher as noted.
The overly rich plugs are interesting. According to Cliff R. he told me to keep the idle mixture screws as much on the lean side as I could and keep a good idle. This should be set while engine is fully warmed up. I have never had much luck with the edlebrochs personaly.
I would take a good look at your distributor and make sure every thing is working good also.
