It sounds you might have a couple things going on. 1. An air leak 2. Hoses connected incorrectly/missing 3. Not running on all cylinders. For the cylinders, put your hand near (don't touch) each individual header pipe to see if the cylinder is firing. If they are REALLY HOT, that cylinder is running.
Before you drill out the remaining piece of bolt and have to be in an easy out, try seeing if you can work the bolt out. One time I had a valve cover bolt break on me before I got any where near the specified torque value. Take a small punch and put it on the remainder of the bolt where there is a little lip from the bolt twisted and broke. With a light taps, you should be able to back out on this lip and back the bolt out to the point of where you can get you fingers on it and get it out. I have to this many times and not had to drill out threads and all. Of course you'll have to remove the stator cover, but it sounds like you're going to have to do this anyway.
Do you have a manual for you to reference and make sure the hoses are all connected/there at all. Sounds like the guy you bought it from might have not cared and cut corners. If not, I'll pm you a link.