No on both counts. Sorry. Although Mirtazapine may help with long term mood disorders caused by meth usage. However, it could take 3-4 weeks before any effects were noticed.
Meth is a drug best avoided (although I do take it). If you must take it, try not to do so without having a benzo and/or anti-psychotic for the comedown. Seroquel is very good since it makes you sleepy on top of it’s effects on mood.
You won't be able to sleep after "snorting meth all day", period. Maybe a benzo or a strong anti-psychotic could help, but other than that I'd recommend drinking a pint of beer and taking a sedating antihistamine. It won't cancel the high or anything, it's just a nice combo to get you ready for a nap at the tail end of a long acid trip or days-long tweaker odyssey, etc.
Mirtazapine might help actually. While its peak antidepressant effect does take weeks to kick in, its sedative effects occur upon single dosing. It is generally pretty safe to combine with methamphetamine due to its antiserotonergic properties. I have personally combined the two pretty extensively.
Hold 15mg of the mirtazapine under your tongue until it dissolves. 7.5mg might work too. It should produce sleep depending on how much meth you took. Doesn't taste good and your mouth will become numb but it works pretty well and quickly via this route.