It’ll break saving books you bought from Amazon, but you’ll still be able to send books you got from other places to it from Calibre. Fortunately barely any of my ebooks on my kindle are from Amazon (though my next ereader isn’t going to be a kindle, that’s for sure).

I put my microfiber cloths in one of those delicates laundry bags and toss it in with a regular load on cold, then let them air dry. Never had any problem with them scratching lenses.