When I first started reading your post I thought fuel delivery problem like fuel pump or maybe debris in the tank. Then as I read more I started thinking electrical. A couple of easy things to check -- fuel pump relay and O2 relay. You should keep one of each in the glove box anyway so no harm in buying them if they are not the problem.
What kind of CDI box do you have? Bosch or PermaTune or maybe MSD? My CDI died last weekend and it was an intermittent failure. One reason I'm thinking the CDI is the tach symptom. One wire in the CDI harness goes to the tach. It sends a square wave at a frequency that the tach reads. If the CDI is going bad it could be sending a bad signal to the tach. Your best bet to test the CDI is to find a local friend with a known good CDI and coil to swap out.
You should also check your battery to see if it is perhaps undercharged or overcharged. Problems with the VR can cause a wild bouncing tach. Does it normally crank strong?
Edit: My CDI died last weekend and I had to get AAA to flatbed the car home. I replaced it with an MSD Street Fire and Blaster II coil on Friday
as described in this thread.