"Quitter's flu" is definitely a thing, but that name is new to me. More generally called cessation symptoms. Not everybody gets it so bad, but it's your body in the process of cleaning itself out from the toxins in analogs. All of the symptoms you listed are related, if you quit smoking without vaping you probably would have gotten the same thing.
I do have a theory that PG can affect the symptoms though. It's bacteria killing and hygroscopic properties seem to jump-start the detoxing process
In my case, it's a definite PG sensitivity. I've tested it several times, since. Anytime I use juice with PG in it, I start to get the same symptoms. It's unfortunate for me. Fortunately, I have finally found some great VG only juices, besides my original vendor. It was difficult to find any who had strong enough flavor.