In regards to 3, I was there exactly the same day and was able to catch coric/kyrgios after the tsonga/nishikori grandstand matches. The trick was two-fold:
1) Leave Tsonga after a set and a half because it was going to be routine against Nedovyesov. Andujar bent over and retired.
2) Watch the women's match (Stosur/kanepi) before the men go on the court. A lot of aussies were really camping that part of the grounds because of the schedule.
That day was really packed, the busiest i've seen it and i always avoid labor day weekend crowds. But that thursday landed right before the holiday weekend and I believe people took the extra days off. They've also expanded the complex, particularly the section where kyrgios and coric were playing that day.
I've been going for about a decade strictly by grounds passes (never went into Ashe), and by far you get the most entertainment for the dollar if you schedule wisely. For instance, it's worth it to watch an even men's match between mid-ranked players, instead of watching some top player swat a lesser being on armstrong/ashe. I also purchase my grounds pass a couple days beforehand in case of weather/wind without any problems.
If you really want to see the crowd-pleasers like wawrinka, monfils, or kyrgios, then you will have to suck it up and watch wta before their match. People just don't have the knowledge or stamina to stick around in between matches.
It sounds like you had an itinerary partially similar to mine for that first Thursday last year. I left Grandstand after the first set of Tsonga's match because I figured he'd win and I wanted to see Serena in action even though I'm not a fan of hers because I'd never seen her play before. Then I stayed in Ashe to watch Djokovic's match (only took 1 1/2 hours). At that point I wanted to go back to Grandstand or Armstrong to see another women's match, but the lines were super-long, so I went to one of the on-site stores instead and bought a couple T-shirts commemorating my first visit to the U.S. Open. After that, I went over to Courts 5/6 and saw the end of Stosur/Kanepi (and the end of the match on Court 6 that I cannot remember; I'm pretty sure that was also a women's match) before working to get a seat in north baseline seats for Courts 5/6 to watch Kyrgios/Seppi and Coric/Estrella Burgos.
With your last comment, I'm realizing that positioning yourself for a match you want to see on the outer courts is critical at the U.S. Open when there are large crowds, particularly in the mid-afternoon. I saw that first hand with the CiCi Bellis match I mentioned in my second post above; the line to get into Court 17 was nuts by the time the Coric and then Kyrgios matches were over and I didn't even try to get in line.
Incidentally, I agree with your other post to a large degree; I purposely picked the day I attended last year (Thursday first week - 2nd round) because of the big names (particularly Djokovic) playing during the day session but also because I figured the crowds wouldn't be as big and ticket prices on the secondary market wouldn't be as high. Additionally, the 2nd round gives you a lot of bang for the buck due to the high number of matches played (similar to the 1st round but probably somewhat higher quality). In an ideal world, I would attend the full second round (Wednesday-Thursday of the first week) with a grounds pass or the full quarterfinals (Tuesday-Wednesday of the second week) with a loge/2nd level Ashe pass to avoid the really big crowds, but multi-day passes for just those days aren't sold by the USTA. I'm starting to realize that buying a longer pass and then only attending some of the days that are part of that pass and selling the other days on the secondary market at a profit may be the way to buy tickets for and attend the U.S. Open. I may try to do that in 2016.