A text file isn't indicative of what you'll get in QLik, since it's storing things in an entirely different way. You should start by loading this into a QVF and see how large it is. Qlik doesn't need to handle your text file, just its own internal storage, and if you have enough memory it should be able to handle the data.
Generally speaking, some tricks that reduce file size include:
reducing distinct values (which you seem to have already started on)
Rounding / flooring numbers if unnecessary precision exists (and explicitly formatting the result to the desired format)
Using autonumber or otherwise hashing out any key fields