1) when you click on a site from Google/Yahoo, the Referrer field will contain your search terms. So any site you clicked on can see what you searched for. Lots of Wiki sites will highlight the words you searched for if you came from Google/Yahoo. On Ixquik, they appear to use POST for search, so sites can't get your keywords.
2) They do use google ads (so Google gets your IP. Big deal, turn off your router for a day and you'll likely get a new one.) But they don't appear to be sending your keywords to Google (don't know if this is policy or not, but I didn't get any relevant ads, only ixquick banners from Google). So even if Google gets your IP, they don't appear to know what you're searching for.