It’s nice to know that someone new to games has been fascinated by adventure games enough to become a frequent player. 
It seems that your girlfriend has a preference for all Amanita Design games. Did the graphic style of Amanita games have a big influence in her choice?
Are you playing it with the old graphics or with the modern graphics of the remakes?
About your questions…
This information has not been disclosed by the developers.
What we know is that back in May they didn’t reach break even yet and that in their last podcast they said that the break even will require some time to be reached. Here is some additional information by Ron on this matter (read also his other posts in that thread).
We don’t know, nothing has been announced so far. Ron said that Thimbleweed Park sales were not enough to start working on a new game right now. They are still working on Thimbleweed Park, both adding new stuff and porting it to other platforms.
About the pixel art that you saw, it was just some fan art. I think that you can safely ignore any news out there unless it’s an article of a well known website that provides a link to the original source.
And, of course, the best thing to do is to directly read the source itself, for example the Thimbleweed Park development blog or ThimbleMail (which is very useful if you have not much time to monitor all these stuff) or these forums.