That's great! Thank you so much for your patience and for taking the time to post your test results.
I didn't mean for it to take this long (achieving 60 FPS was quite challenging), but I think the performance improvements were worth it in the end.
Regarding native UI framerate issues, I've only noticed serious framerate issues when giving a TextBox the keyboard focus or when pinch zooming a WebBrowser control. Interestingly enough, giving a text field within a WebBrowser control keyboard focus does not cause a framerate issue. It's really hit-or-miss. But I suppose it's not that big of deal since you probably wouldn't display native UI during gameplay and only in static screens within Corona.
I'm currently working on the native/Lua bridge API now. I expect to have it done by the end of this week (worst case). Hopefully sooner. Also, I still plan on looking into the "applicationSuspend" issue that you've mentioned with the Start/Home key.