I think the tooltip thing is a bug, thanks for reporting it.
For now, you may want to just turn them off – there’s an option on the settings screen to just turn them off.
It sounds like you got things working, but if you want help with the widget please provide the exact query you’re using. There are a few examples in the documentation, but note that for the widget you just write the part that would normally be in ‘show_query=”” ‘ (without the quotes).
By the way, that mashup shortcode also looked like it’s missing quotes in the show_query part:
[mashup width="875px" height="375px" show="query" show_query=meta_key=featured&meta_value=yes&posts_per_page=-1]
[mashup width="875px" height="375px" show="query" show_query="meta_key=featured&meta_value=yes&posts_per_page=-1"]