As of version 0.50, I think the highest-heart scene to do is the buttfuck in her "showing butt" pose. You don't need to get the reds to get enough for it, but getting them on the earlier easier ones certainly helps you not need to get gold on the longer, more difficult ones.
Yeah, that's a great idea! Although I'd only worry that you might accidentally miss a scene if the "most recently added one" said that it's the highest you can reach and you just stopped playing at that and missed a scene, and it'd probably be a bit time-consuming to program in a tracker to track whether or not you've seen each different scene.