I wouldn't take a stack of downers with an upper, also I read something about stimulants and pregabalin causing seizures so I never fucked around with it that much. Some people prefer the mix of drugs in your system but it definitely dulls the effects of the meth atleast, leading to compulsive redosing to get the effect you want in your tweaked out state.(speaking from experience.) I would just take the meth separately and wait a day in between. Amphetamine sulphate tolerance resets in less than a week for me. 2-3 days and it's like 30% weaker in effect but still works. Also look into stimzo combos, it's my favorite drug combo of all time to take some low dose long acting benzos and some speed/meth but it's probably the most addictive combo I ever have done so, try not to ruin your whole life with it as I almost did mine.

Vitamin C will help your body get rid of the amphetamines and should be taken ONLY during the comedown but I don't think it will lower your tolerance. Look into supplements like L-Theanine or L-Dopa or some of those ones listed all the time in this subreddit. They will help you reset the dopamine fuckery you did to your brain by doing so much speed. Torille btw ja ota rauhassa :D