Hey scoobie,
You've got a lot of honesty working for you. Doesn't the Bible say that those who worship God must do so in spirit and in truth? Humility and honesty are better routes for finding God than simply "having answers". You are further along than you think.
As for leaving/parting remarks... the compliment and excuse-yourself routine should work well. But if anyone gets pestering you as to WHY you would give up studying, give them this website
http://www.un.org/dpi/ngosection/watchtower.pdf
and tell them that you can't imagine any good reason for the Watchtower to join what they consider The Scarlet Beast... If you are a brave sort, you could really begin asking innocent questions, and bringing stuff from online to them and ask (sincerely) how these things could be explained. Hold your ground in requiring solid answers. If they can't/won't explain these things to you, you have a problem with studying with them. Remember: it is YOUR destiny, not theirs.
BTW: My sister-in-law is an ex-Mormon, and it is a lot of the same thing as the witnesses, just different issues. I would NOT recommend them! ...Perhaps that little survey you took reveals that you are more compatible with authoritarian tendencies. Did they put down, as far as Mormon doctrine, that "worthy" Mormon men could become gods with thousands of wives and their own planet to populate, and women are resurrected to be the No. 1 wife of their earthly husband--now a god--IF he calls her forth from her grave?... There is a LOT of hidden doctrines potential converts are shielded from in cults like these. It's only when you have publicly declared your faith to everyone (and risk looking foolish) that you begin to learn the "oddball" stuff. ...
And finally: this thread is an encouraging one. You've got excellent advice and insight from ALL sorts (save one ). Would that more and more new 'JW students' would wander here and quickly understand what is being hidden from them. Good for you, scoobie!!!!
bebu