Yes, you can process your apple butter the same way you made sauce. It is, after all, just thickened and spiced sauce.

Yes, you can stack jars in your canner (used as water bath), as long as you have a rack between the layers. You don't want a jar sitting directly on the lid of another jar.

I'm not sure how you plan to cook down the sauce into "butter", but I have found the crockpot is good for small batches and a large roasting pan in the oven is good for large batches. No scorching! I am not good about standing over a pot for hours on end!
In the oven, you can ignore it for 30, 60, 90 minutes with no problem! Depending on how high you have the heat.
I usually cook down at about 275-300 and stir every 30-45 minutes.

Deanna

Thanks! I usually just cook it over the stove. But I just realized I don't have apple cider...so I'll have to wait for another day.

It's your choice of course as long as you accept that unpeeled adds additional bacterial and mold risks. That's why peeling is what is recommended by the standard guidelines.

Personally I can't relate to apple peels in either if I was making them.

Dave