1. 30ga wire is recommended because it is very flexible and easy to solder to small points. Solid core cat5 is some brutal stuff to try to do small-scale soldering work with. If your skill is up to it, then use what suits you. A spool of 30ga wire is only like $7 at RadioShack, tho. Worth it for the lack of frustration IMHO, but do what you like.
2. read the nand 3 times, then use one of the numerous tools to compare the dumps. I personally like Nand Healer GUI because it automates the process (will dump the NAND 3 times, then compare and even check for JTAGability automatically). If 3 16meg dumps all come out identical, chances are that they are good dumps.
Hope this helps!