The Terms of Use does not restrict the distribution channel of any
app, unless it violates a Terms of Use section or other restriction.
In other words, it doesn't require distribution through the Android
Market; you can use any market, as long as the use of a market doesn't
violate something else (like copyright or some local law). There was a
thread on this a while back, but I can't find it right now.
If by "support" you mean some level of support services for meeting
Google Chrome Webstore guidelines, then that is something you should
probably not expect (from AdMob or any other ad network). Whether your
app/AdMob ads are in compliance with a distribution channel is for you
to monitor and determine (including Android Market).
-Jim