Seems like a decent game, but doesn't support zooming at all so I'm left with a tiny play area. I would love to bump the score up by a couple of points if you make it work though.
The recent update added some indicators to the upgrade screen which mark the cheapest upgrade (as well as others which are relatively cheap, compared to your most expensive upgrade). It's not exactly a "cheapest upgrade button", but it should address the same issue.
If you're going to be adding to the skill tree, and especially if you aren't going to make enough goals to max it out, you should be able to reset your skills.
I get the username straight from the Kong API, and they do not allow for custom 3rd party login so... no idea.