For the Count and Compare import CSV file:

Q1. What is the character limit for each of the 4 import fields?

A1: Item, Location: 100 characters.
Description: 255 characters.
Quantity appears to be a 64-bit unsigned integer, so the numeric limit is just under 4.3 billion (4294967296).

Q2. Is there a limit to how many items can be in import file? (based on the character limit if that affects it)

A2: There is no known limit.

Q3. Is there a limit to how many different locations can be in the file?

A3: There is no known limit.