Steven,
I don't have direct experience with that particular car, but I do own a
Reatta which has given me a bunch of electrical surprises, and maybe
some of what we Reatta owners have experienced could help you.

The Reattas have battery cables with up to 3 separate cables going
to the battery. One goes to the alternator, one to the starter, and one
to the electronics.

These cables often corrode internally, and lose contact.  You can,
to some degree or the other, peel the covering off the battery terminal
end of the cable and clean the individual connecting surfaces.  Maybe
yours is similar.  This could be an explanation for the 4 ohms resistance,
which is quite a lot in a circuit like this one.

The starter cable does not go through a relay in this case, but the starter
solenoid voltage does.  If the theft deterrent system is activated, the
starter solenoid does not work.

I had some custom cables made for my car, since I didnt want to pay
the price GM wanted nor did I want the same type of technology.

Maybe this does not apply at all, but hope you solve your problem.

You are describing a bad connection.

The main 10 ga alternator wire goes to a 14 ga fuse link wire which
bolts onto the starter solenoid.  Very likely the connection at the
starter solenoid just needs to be cleaned.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's