My suggestion was to try transposing the Software Instrument track to different keys and singing along LIVE, not recording your voice in different Keys, and when you find a Key you like to sing in, then record that. But you're not even listening to the Software Instrument track when you're singing & playing back, so apparently my suggestion would not be relevant to what you're doing, so ignore it. I guess I really don't understand what you're trying to accomplish with the Key changes, so I can't really offer you advice on this. You previously described an approach you thought would work for you, why not just go with that..
If you change the Key between recordings, then all the Regions are going to be transposed every time you change the Key, whether you want them to be or not. It seems like you're treating the Key setting as if it's tied to each particular recorded Region, but that's not how it works -- it's Global, it affects all Regions at all times. And I'm not sure why you're doing that -- changing the Key and then recording does not change the sound of the resulting recording -- a Key change only changes the pitch & sound quality of already-recorded Regions.