Snorting - Limit to amount one could theoretically snort?

[blipblop]

A few questions.

1. The character in the story I am writing has a large supply of ritalin 10mg tablets.
If this character was to crush the ritalin and snort it, is there possibly a limit on how much the nose can actually absorb at a time?
This character would be dividing the dose across both nostrils.
Can someone provide links/ info on how many tablets would still be producing a stronger effect and not just sitting in the nose not being absorbed?

2. If a character in my story was to be snorting ritalin with a straw, how far into the nose would the straw be inserted? I was planning to write that the character gets the straw about 1cm/ half an inch up the nose, is this accurate?

3. Nasal drip. Is the post-nasal drip a sign that the character in my story is snorting incorrectly? Correctly? Or is this just what always happens regardless of method?

Thanks a bunch.