It sounds like the first problem is related to the second problem. If the app is capturing the position of the top of the current page rather than the actual scroll position, then it would never capture a position past the top of the last page. However, the workaround should let you scroll past the top of the last page to reach the end of the document.
You didn't say what platform you're using, but I only see the problem on iOS. If you have an Android device, you could record your automation tracks there, and they will sync back to your original device, with the sizing and positioning scaled automatically.