Wow... I cried a little just now hearing that you dumped 5 gallons of cider down the drain because of a rotten egg smell...
First, 3 weeks isn't nearly long enough for cider... it should sit in primary 2-4 weeks, then rack to secondary for another 2-4 weeks... after that, you can either bottle or rack again into bulk aging for 3-6 months. Cider is quite different when it is young (or in your case, unfinished) compared to aged (even if for a month or so). A good cider (not Woodchuck) should taste like a good white wine, but still have a good bit of apple flavor left. Remember, RDWHAHB, cider takes a while...
Also, the potassium sulphate should not have sat for a week. The mold on top was probably a really bad sign. If you are going to sulphite (campden, K2SO4, etc.) it should only be for 24 hours before you pitch.
As far as books go, there are a couple that I would recommend if you are seriously interested. The first is $4, and a very good 'intro to cider' imho, check it out,
Making The Best Apple Cider.
The second book I would recommend, I just finished reading myself, and is a much more in depth look at making cider...
Cider: Making, Using & Enjoying Sweet And Hard Cider.
NOTE: Both links forward to HomebrewHeaven.com, just because that's where I bought them from, I'm sure you could also find them on Amazon or Half.com as well...