1) I know that Flutherbot (Fluther’s IM helper) tells you when there are new questions for you via IM, but I don’t know if you can answer them from IM. I don’t really use Flutherbot. You might want to set up your IM account with Fluther (the settings are in your “My Account” link, then click on “IM Settings”) and fiddle with it to test. P.S. – I do think you can ask questions from IM though.
2) @dverhey pretty much answered this one. If you want everyone to see the response you can do what he suggested. If you only want the poster to see your response you can click on “Thank (user name)” and it’ll take you to their page where you can write them a PM. Checking the public/private box makes it publicly seen b other Jellies who view that persons page or not, depending on what you click. FYI, the “Thank (user name)” button only shows up on questions you ask, but you can always click on the users name or avatar to get to their page if you want to send them a PM anyway.
3) To find questions you’ve asked and answers you’ve given, go to your profile page, scroll down and you’ll see a list of 5 of each. If you click on “Browse more of (user names) questions/answers” you’ll see more.
Welcome to Fluther. =]