Not getting 12 volts to coil

Don't lead yourself down wrong paths. You are changing the circuit (wiring) and it is giving you FALSE results
The system will not work/ won't run with ECU ungrounded.
When you unhook the coil NEG of course the ballast shows 12---the ECU wire going to coil NEG causes the coil to draw current through the ballast resistor and that pulls the voltage down....just like it is supposed to

Measurements

Measure coil POS with key on/ engine stopped. (and everything connected normally) Should read somewhere 6--10V. If it reads 12 either the ballast is bypassed or the coil is not drawing current, meaning "some ting wong"

If that is OK, disconnect dist. pickup wire. Again with key "in run" take the dist. connector engine bay end, not the dist end, and repeatedly tap the bare connector pin onto ground. Use a test gap/ spark plug connected to coil tower. You should get one single "snap!" spark each time you ground it

Next, clip your meter to coil+ Crank engine USING THE KEY. You should get "same as battery" during cranking. In other words if battery reads 10.8V during cranking, then the coil+ should be about the same. If it is quite a bit lower or zero, the brown ballast bypass circuit is not working

If that is OK, check spark with test gap at coil tower crank and test using the key. If you get no spark, and the earlier test with the dist. connector did, then you may have a dist. pickup problem OR THE CONNECTOR may not be making contact which is common.

Inspect the inside of the dist. around the pickup / reluctor for rust/ debri, for strike damage, and check dist. shaft for wobble/ looseness. Work the dist connector in /out several times, to scrub the terminals clean, and to "feel" for tightness. Inspect the connector terminals with a lamp to check for corrosion. Same deal with the ECU connector ECU MUST BE GROUNDED