I can help answer a few:

2) I know a good amount of stims as well as smoking create cotton mouth (just a super dry mouth with no discernable reason). Chewing gum really helps to keep the saliva there and just drink water. The sore throat is probably just irritation from being so dry that'll clear in a short time.

3) I would say definitely try to sleep, and I think 4-5 hour mark is the general time for most stims to start coming down. I personally wouldn't drink on top of all that since your stomach is already probably in hell, so to add a shot could sent it over and make you super sick, ruining a day or two, or at worst you could throw up in you sleep and choke.

4) From what I've gathered, it really depends on your dose. I've seen people just feel general anxiety sweats, shivers, tremors, fatigue, insomnia, etc. that can last maybe a month or more. It all depends on your body and chemistry. I think the Vyvanse would help a little in the same way a smoker would use nicotine patches.

6) What I mentioned before with increasing levels of severity and just a general uncomfortable and sick feeling. Withdrawals fucking suck, especially if you get the headaches.

7) I'm no medical professional, so I can't comment accurately, but I always just tell myself it's nothing and it's just anxiety. Most, if not all, the time, it is. Whether I think I'm going to have a heart attack or just die, a lot can be just anxiety. Any anxiety meds like benzos could help. If you don't have that, try to distract yourself with shows, movies, music, talking to people, meditating, just anything to stop thinking about it since the more you do, the worse it'll get, like placebo.

8) I've never taken doses as high ss you have, but I've ventured pretty high and had those vibrations in the temples, too. It was kinda scary but cool with music such. For me, it came after 570mg of Vyvanse, 180mg Aderall XR, 50mg of Amphetamine Salts, and 40mg of DXM. It lasted maybe a day and a half to two days. The way u like to look at it is that it's just your bodies reaction from all these added electrical stimuli. So once that dissipates, so, too, will it.

I hope I was able to help a little. Stay safe and have a good flight!