Overcharge now low/no charge

Ok folks asking for some help here. 1972 Duster slant 6 grandma car. No signs of hack job wiring. Only thing modified is h4 conversion headlights and a pertronix set up in the dist. From previous owner.
Last week noticed ammeter would peg under high idle and would climb and drop with throttle. Parked the car and started reading. Found a few threads about Overcharging and Voltage drop along with the MAD mod. Didn't have a multimeter at the time but started following my wiring. Pulled the bulked head connector, cleaned it, cleaned and replaced VR with mopar VR, had a Chinese one, cleaned VR connector, wirewheeled coating and sanded firewall for grounding. Cleaned starter relay. After all the cleaning I noticed the black wire from ALT. Connector in bulkhead started to melt. Followed it through the firewall to find 8-10" of melted black wire in cabin. Followed it all the way through the dash to make sure to cut out all the bad.
At that point did the MAD mod. Ran new 10g wire from ALT. to battery relay with fusible link. Bypassed bulkhead and ran 10g wires straight through. Spliced ammeter wiring together with fusible link.
At this time I ask my neighbor if he's got a multimeter I could borrow and he does but I've never used one of these things and he headed out of town. Read up on how to use it, I think, and I assume I'm using it correctly but we all now what happens when you assume.
I realise I have no b4 testing to compare to but here's what I have found and here's the multimeter I'm using and setting.
New battery (2weeks old)

@ battery, probes to + and -
Battery & engine cold, sitting 2+hrs: 12.05v
Key on No start: 11.5v
Start engine, high idle warm up: 12.12-12.13v

Engine @ operating temp and running
Negative post to VR body:
.87-.90 mV @ idle
.20-.23mV @ high idle (1200-1500rpm)

Key on No Start
Black prob to blue field wire, red probe to + battery
9.23v slowly climbs to 9.55v

ALT stud to + battery
55-57mV

After doing about test, 30-45min checked the battery again and its @ 9.56V

I'll put it on the charge and let it trickle charge tonight

Key on No Start
Black prob to blue field wire, red probe to + battery
9.23v slowly climbs to 9.55v

!!WOW!!

What you are measuring here, if you did this correctly, is the functional path from the battery to the blue wire

In other words, battery-----fuse link----through the bulkhead---through the ammeter--to the ignition switch connector---through the switch, back out the switch connector----back out through the bulkhead connector and this is your "ignition run" IGN1 buss, which supplies

ignition system, VR power, blue wire to alternator field, smog equipment some years

You should be showing very little voltage at those two points

Another way to double check this is:

With key in run, hook one multimeter probe to ground

Measure battery + and then measure your blue field wire. They should be close to the same. If not you have a huge bad connection in that circuit somewhere, and certainly would explain "no charge"

You can download aftermarket diagrams, and factory shop manuals for free from MyMopar.

Thanks 67Dart273! I'll double check it after the battery has charged a good minute. I did find some schematics. I've been reading every thread involving voltage drop and no charge situations for the past 4 days and my heads starting to spin! Thank you for some direction on this

Ok let the battery trickle charge all night. Voltage @ battery 12.48 key off

Key on No start: battery @ 12.12v
Negative battery post to Blue field wire @ ALT: 11.25v-11.28v
Positive battery post to Blue field wire @ ALT: .79V- .81V
Positive battery post to main black wire @ALT: 60.7mV

Car running, high idle, battery @11.9v and slowly draining about .1 volt per 30sec.
Neg. Bat post to blue field wire: 11.29-11.31v
Pos. Bat post to blue field wire: .78-.80v
Neg. Bat post to VR case:08.2mV

Just an update: got everything figured out, pulled the alternator off and had some small parts fall out. Got one from the parts store and everything's good now!