Stalling in a hold should not be a PC event. Stalls, yes. Holds, yes. Stalling from a hold, maybe. Maintaining a hold while stalling, no. Was it an MV by chance? Sounds like not if no retraining. Reason I ask is that if you tell that story at an interview it *might* raise eyebrows, since none of those folks will have ever heard of a stalling & holding PC event. So you might want to come up with a way to rephrase that story. Was that your one-year PC?
Re. the fed ride: Dude what were you thinking??? The fed is not there to evaluate your on-time performance or block-hour padding. Ok, sorry had to say it. That one should be a straightforward lesson-learned about judgement and priorities.
The above comments are what pilot interviewers might be thinking.
The problem with two 121 busts is that, unlike GA, 121 training/checking is *relatively* consistent. So they might tune out a 91 bust or two as background noise in the distant past, but 121 busts are a bit more concerning. In both cases sounds like you were pretty inexperienced in your seat, so that helps. Five years in the past helps too.
I kind of doubt DAL or FDX is calling anytime soon, they can be picky. But things are trending in your favor with retirements ramping up faster than the system can replace them. I think you'd have a shot somewhere in the big six eventually.
My gut feel says 4K TPIC is a hair low in your position, so maybe stick around for another 2K and see what that gets you? Right now, I think you stand a better shot getting hired out of the left seat of an RJ than the right seat of a LCC. I had expected that to have changed by now, but I'm not seeing it.
But depending on where you are in life, might want to just get the move over with and settle in for the long haul. Most of the LCCs will provide a pretty good life by most standards (better than regionals), and they are all getting pay raises (real ones, not regional chump change). Also need to consider when your last type rating was... more than 3-5 years and you might be "stale" for the big six.
Get some interview prep if you haven't already.