83 B2000 won't start after carb adjustment

I took my 83 B2000 into a shop to get it to pass emissions, it passed, but they had to set the idle mix wicked lean and it ran for crap after - engine was lurching at idle and was stalling on turns. Got it up to temp and tried to adjust the mix screws on the Nikki carb. Sounded great, got the engine running a lot smoother. Let it sit for a couple hours and wouldn't start up. The choke isn't the best (and is going to get worked on soon) but it hasn't had any trouble starting before. It'll fire up and run if I have my foot on the gas, but as soon as I let off the RPMs fall and it dies. It seems like it must be a problem with the idle mix, and I tried turning them into a couple different positions to see if I could get it running again but to no avail. Don't know how to adjust/troubleshoot without the engine running.

Thoughts, tips, ideas?

Typically, idle mixture screws turn counterclockwise to richen the idle mixture, and clockwise to lean out. Yes, typically carburetors are leaned out to better pass emissions. So New Mexico, with very few people in a large state, still checks emissions of a 1983 vehicle? How sad, and what a waste of time, like swatting a fly and hoping the world population of flies decreases (yes, technically, it does: decreases by one).

But while it's cold, take off the air cleaner top, stomp down once on the gas pedal, and see if the choke butterfly is mostly horizontal like it should be when cold.

Choke should be mostly vertical when the engine is warmed up (10 full minutes of running).

I'm not an expert on these carbs but generally you turn the idle screw all the way in then turn it 2 turns out and that should at least get the truck running so you can fine tune it. The problem may not even be the idle mixture setting but its a good place to start.

Getting to the root(s) - the carb is adjusted all outta whack, and the choke is a bastard, BUT the bigger issue seems to be a really finicky connection on the fuel pump regulator fuse. Any tips on troubleshooting that?