I am still laughing at your post Gary - well written.
Mind you I am not dead, can't rule out re-hab at this point, and live in Canada which is close to Sweden latitudinally speaking....and I like to think I am a small "e" expert.
Jack some good points are mentioned by Gary and others. Here's what I would do. Remove all vacuum hoses to the manifold, and plug them with duct tape (will work for a while) If you have secondary throttle plates, remove the shafts and put pipe plugs in the holes after tapping them to receive them of course. If the manifold gasket is good, and the ignition timing is good, then the vacuum should approach 20 inches at idle.
The crankcase vent uses the fitting which has a small drilling in it, about 1/16 inch, whereas the power brake fitting uses the large bore one. They look much the same on the outside. If those hoses get swapped, the manifold breathes nearly unrestricted through the large bore one, and the booster still gets evacuated, but slowly. If indeed those hoses are misplaced, and they may be, your problems are soon over.
Like Gary says, you have to keep at it.
And I think the B20 has more bearing area than a SB Chev, let alone the B30. Of course the B30 WEIGHS as much as a SB Chev, which is not a good thing.