Convoluted is right.
1) This is correct. I believe there were more than 200 at one time, but by the time the merger snap shot happened, there was around 180-200 who had AA seniority numbers, but had never actually been a mainline pilot.
2) Pretty much
4) The "midatlantic" guys came in a couple different varieties. When MidAtlantic was formed, which was a B scale or worse scam, it was known as Midatlantic but was flown under USAir certificate and callsign. It was staffed by furloughed mainline USAir pilots first, and the rest of the ranks were filled with pilot from wholly owned subsidiaries like Allegheny and Piedmont (the Dash8 airlines). When those pilots came over, they werent sold that this was their pathway to mainline or that they were taking a job at USAir but only MidAtlantic*. Around the same time US/AW merged, Midatlantics airplanes were sold off to Republic, and some of their pilots had the option to follow the airplanes under a J4J agreement. Some did, and some stayed and gave up their recall rights (woops). It wasnt until the America West that they were suddenly tacked onto the USAir East list and become "one of ours". There was some battles along the way with LOS credit for time at MidAtlantic (so was I mainline or not?), but at the end of the day, those stumbled upon pretty good mainline seniority if they were relatively young, came over from a DH8 no questions asked, and now will live happily ever after with AA. Of all the people who got bad rides in the 2000s, I dont think they had the worst. All this stuff is in the rear view mirror and really isnt discussed much anymore.
*This is how it was described to me by an honest pilot who was involved.