It cannot limit the number of tags displayed but instead you can set the minimum # of occurrences of a word for it to be displayed.
As for the search form, I agree it would be nice if it linked directly to the page except there is one problem with this, most of the Tag Words occur in more than one document. So instead each word links to an AjaxSearch results page and makes that Tag Word the search word, displaying all the docs it occurs in. An example of this is on my site
http://salscode.com.
Here are my two calls.
Here is the Tag Cloud call, listing the parents, the minimum # of occurrences to be displayed and the landing page ID.
[!Tagcloud? &parent=`4,38,28,48,3` &min=`3` &landing=`64` &lang=`en`!]
Here is the landing page, Doc 64. I put the same parents so it would search the same docs that the tag did.
[!AjaxSearch? &ajaxSearch=`0` &parents=`4,38,28,48,3` !]