Thank you so much for your kind words! It's just the two of us here (one artist, one programmer) so unfortunately we had to make do with the music we could find but we'd have definitely loved to find something more fitting. We agree with you that it doesn't sound very mousy!
The green outline should appear around a building when a quest pops up, and if you build it in time you'll get an extra reinforcement denoted by the speech bubble. We've had some feedback from others that it's not too clear so that's something to improve next time!
In terms of the balancing, this is the kind of game that would require endless tweaks and it could definitely be improved. In your exact situation however, the button price of the tailor increases by 0.5 every time, so for it to cost 6 buttons you'd need to have built 10. This gives you a cap of 33 thread, more than enough to afford a third jeweller. If this isn't the case, you've probably run into a bug - sorry about that!
We really appreciate the feedback!