Unless you find a nest hiding in the airbox intake, it's hard to imagine air starvation as long as the air plate floats easily and the exhaust isn't plugged. My chief suspect at the moment would now be a stuck plunger in the fuel distributor, as you've previously considered. It's not that uncommon, even more so with yours having sat so long, and would very much correspond to your symptoms. Manually lift the air plate and if fuel flow to an injector doesn't noticeably increase then it's stuck.

The exhaust gas smell might simply be it's running too rich at idle. Conditions have likely changed significantly since the fuel distributor was last adjusted. Unfortunately with new plugs and minimal operation since getting it going after all these years, there's not much point in reading the plugs for additional clues. I'm also wondering if unburnt fuel dumped into the system during some of your testing may now be gassing off with a warm exhaust, in which case it may be a short term issue and the smell should soon improve.

I hate to think how many hours so far in refurbishing the tank and fuel delivery system. It's got to be a bit frustrating having it now running again and getting a big stuck chasing the likely last remaining issue.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now