I think the compression would still show good with one tooth off on the timing although I've never tried it. It's just that the bulk of the compression is at the wrong time so the reading is only a fraction of the right amount. If it was a constant compression leak it wouldn't (obviously) run at all. As a result, the entire vacuum reading is poor although as you know the individual compression readings are good at that moment. try corking all of the hoses that aren't required to run, at the throttle body or intake manifold, and see if it starts better.

I'm limited in B21 knowledge, but if you take the bottom pulley off again, you can index the timing belt. Re-time with all the shafts and put it back together. The bottom pulley/gear index mark on the block is TDC--and set everything else to match. Don't bother pulling the head again. I remember doing a few B21 timing belts and they were easy & quick. I'm sure there are marks that index the crank.
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1992 940 wagon, 77k
as well as others.