With a 5 mil undercut, you use about 12 ml to coat 1 square foot and with 120 ml of 10% gelatin that is about 1000 mg / square foot. My statement above was too vague. The range for gelatin in this case would be from 500 - 1000 with an average of about 750. I coat between 5% and 10% so therefore the average is what I gave, not the exact value.
As for alcohol, it should give no hardening effect whatsoever. You need alums or aldehydes as hardeners for home lab work. There are others, but they are generally too toxic for our use. Alcohol has a mild surfactant and anti foam property.
I would guess that the clays in the paper are adding some hardening effect, but the paper is stripping away from the emulsion due to poor adhesion.