Wish I could help answer your questions about the transfer case and auto shifting. My only relative experience that you had is that I have not experienced any up shift at all from my auto tranny while riding in 4-Lo. Then again, I'm always crawling slowly on rocks with mine in that mode.
I remember reading your post about your aluminium radiator upgrade last year but, I can't recall if you installed an aftermarket transmission cooler? If you are still running the cooler lines through your radiator, your tranny will be basically the same temp as the engine coolant. I know this dose not help you much, sorry.