1. What does "3ii" mean?
   
is equal to "OUNCES"
What looks like a "3" is not really the number 3, but it's a symbol that means "ounces".
The "ii" that comes after is the roman numeral for "2". So "3ii" means "2 ounces".
Likewise "3i" means "1 ounce", "3iii" means "3 ounces", "3iv" means "4 ounces", etc.
If you see "3ss", that means 1/2 ounce, with the "ss" being a latin abbreviation.
   
is equal to "DRAMS" (aka "DRACHMAs")
On smaller bottles, you may see a slightly different symbol that looks like a "3"
that represents "drams" (one dram = 1/8 of an ounce).
So in this case, "3iv" would mean 4 drams, which is 1/2 of an ounce.
Source: Wikipedia (search for "apothecary system" on google)