SUCCESS!!! Wow that was over 10 hours of work spanning more than a month. That last bolt was a pain. You can see it from below but not access it. Conversely you can access it (barely) from above but not see it.
In this picture you can see my 15mm wrench bottom left, other end is on the bolt that needs to be removed (not just loosened) in order to relocate the trans dip stick. The bolt faces the firewall right near the front-most O2 sensor wires, and you want to look for the same shiny black color of the filler neck.
Now on to the task at hand: Why was this engine ticking.
In short: removing this valve cover was a complete PIA and I never want to do it again.
Thanks for posting your trials; I'm sure it will help someone in the future. It seems like they could have mounted the Pentastar about 2-3 inches forward from the firewall and still had plenty of room in the front, but I imagine it has more to do with weight distribution.
But whoever decided to put the PCV valve back there with (blind) torx screws needs some kind of punishment. The 2011 had three, then the 2012 it was reduced to two, and after I lost one and ordered a replacement, it was changed from torx screws to standard bolts. So there must have been an uprising from the shop mechanics.
Ok here's an update and a tip. In order to find my loose rocker I had to remove the spark plugs and (with 27mm socket) crank the engine by hand. That was pretty cool to see what the valvetrain does.
At any given time most of the rockers are pinned down somewhat so it took some rotating and jiggling but I found the bad one and got it in!
After torquing all the caps back down another check found another loose rocker, but when I replaced that one as well it still seems loose and the rocker that came out didn't seem to have play. So a bit of a mystery but at least I found one clearly jiggly rocker arm and swapped it out.
Reassembly should be a pain. Perhaps not every single bolt goes back... In particular the engine to transmission bolt that went through the transmission fill tube may just never go back in.
Literally made an account just to post a comment. Honestly man thank you so much for this write-up and your trial and error. SO right about how that one bolt to remove the tran dipstick is only accessible from the top with no sight, and not accessible from the bottom but you can see it. WHAT A POS. Literally took an entire day to get this thing off - terrified of putting it back on. Maybe Ill just leave it!
Was never going to actually do this for the rocker arm, but my spark plug seal started leaking and I need to take the cover off to replace the gaskets anyway. Inspired me to just do the rockers while I'm at it.
Any problems since? Anyway, thanks again, all the best!