OK the auto door handles not operating is a good way to get your attention that a new battery is needed soon before you get stranded. Put in a new battery today and the auto door locks/unlocks continue to work good and as a bonus the auto start/stop started working. I do not know the lowest v the door locks don't work because I did not think to check the battery voltage while they were not working for 2 days. The auto lock/unlock did work as low as 11.99v, but the auto stop/start did not. The auto stop/start started working with the new battery at 12.53v.
I went ahead and put in a new battery for the fob even though I do not think the fob battery was low.
I did let the Ford dealer install the battery just in case I needed to have a "just out of warranty" repair but luckily it did not come to that and I only spent about $80 more to have them install the battery than the Costco battery (uninstalled) with the same battery warranty. There is a YouTube on the installation of the battery the positive terminal is more complicated than just taking the clamp of the post.