Hi edog45,
Thanks for the update.
A little stiffness may be connected to sleeping for 12 hours … especially with less movement for that long … but of course your ongoing experience will tell.
It sounds to me like you and your mattress are quickly becoming “good friends” 
Post #7 here and the other posts and webpages it links to may be helpful for choosing sheets. If you are looking for “soft” then stretch knit jersey sheets may be a good choice or some of the viscose materials such as bamboo also have a very soft “feel”.
Phoenix