From what I can see, BTW< the #7 plug may be oil fouled... not quite a good enough pix. if so, then one temp fix for the plug oiling is an adapter that helps limit fouling. It doesn't fix the real issue (rings or bores) but is a way to make it fire better for a while. And BTW, 85 psi compression dry is not a 'dead' cylinder, but is getting pretty weak.
With this engine being all original, sticking piston rings is a possibility, Maybe a teaspoon of Marvel Mystery Oil in that cylinder, and sitting for a day, or an application of Rislone, might help. Probabilities are not high that this is the issue, but does not hurt to try.
BTW.... 25 in vacuum at idle is super high.... actually too high. Sure you are reading the gauge in inches of vacuum?
