I guess it depends how much time you have and want to do lounge hopping on the departure flights. Personally, if I get to the airport 2 hours before INTL then I can go to one lounge for a bit and then before the flight pop out and check out the airport if it it's a new one for me.

Also depending on your terminal you may only be able to check out a single one as it is.

1) From what I remember I think that the United Club at SEA was recently redone and is supposed to be nice.
2) I still haven't figure out what all the EVA lounges at TPE are. I will have 3.25h there in the spring and my only concern is about a shower after coming off the JFK-TPE flight. From what I've heard more or less they are all pretty similar.
3-7) No info
8) I think in SIN your best bet would be for sure the SQ lounge.
9) I'm pretty sure you'll have to leave security for the NH Arrival lounge which I wouldn't worry about...the Business lounge will be fine, plus it's a cool airport to check out. You'd have access to the United Club but I wouldn't waste my time.