we'll I'm not 100% sure but i think if you send your url to 10 people in 1min you'll be kicked out the chat room, if you take your time with every1 you chat with then send your url to them then there's no harm..
What can i say is direct traffic is not so good, it might risk your account if the CTR from direct traffic is too high
yes. if you spam the rooms, Google won't like it. don't try such things. Google can detect such spam very easily.
Instead of Using Yahoo Chat rooms , You can submit your stories to Yahoo Buzz , You will get traffic and backlinks too ! May be Adsense block you using Chat rooms for Spamming
Besides the spam in those rooms, no one clicks the ads, we just block them and report them. Its a waste of time.
it doesn't seem to violate any of the Adsense rules but you are receiving ethical answers. You can drive traffic to your site any way you want as long as you are not telling them to click the ads you're doing fine. Google has algorithm to measure who were or were not told to click ads. There are many factors involved.