Hi Dan,

So sorry for your pains!
I will try to think and talk through some things with you to see if we can shift out thinking into another arena of logic!

Well since it’s not a Diesel engine, cutting off the fuel or throwing a sock in it, you’re out of luck for finding that to be a cause for this stopping.

It is either fuel or ignition, since it runs and you get both over in the start position!
I wish I knew what was not connected that is getting bypassed over in the start position?
This is electrical. There is a orange wire in the AMM connector that you need to put a small test light on.
This orange wire feeds power to the whole circuit of the AMM and fuel injectors and comes from one-half of the system relay. I know you changed it and apparently it works during cranking but I think we need to observe if it’s dropping.

With this clue, That makes it more of the ignition switch a suspect as it’s the last thing that moved.
I’m trying to figure out what’s dropping out.
The instrument cluster goes blank while cranking, except for the alternator as system light.
Voltage does drop way down and all that is expected.

What happen with the instrument cluster at the same time when you release the key?
What happens? Does everything come back on bright quickly?

Could there be a bad connector under the dash that goes to the EZK system from the ignition switch?
Art has brought that up before with a picture of a connector that was kinda yellow?
But does it come from the ignition switch?

Did you replace hoses on top of the heater core or around to the heater valve?
Anything like that in the past?

Phil