More Amazon Qs

It won't let you 'delete' your uploaded document, but yes you can upload a new version in a different supported format if you want. I do not know if KDP Print paperbacks can be preordered.

But, getting back to the Mobi version, if you don't have graphics or complex formatting issues, then you are better off sticking with the Word format, particularly given that you are also going to do a paperback, where you will need to produce a book formatted PDF for upload.

I would suggest looking at threads about pre-orders on the KDP help forums. They can cause lots of problems.

Why is it taking you so long to format your MS for Amazon?

There are templates available on KDP, so all you have to do is copy your MS and drop it into the template. After that, you set up the front matter, get the TOC right (chapters start on odd number pages), if you want something fancy for the chapter title you just modify the existing header in MS Word, and then you set up your back matter.

The first time I did this, it took me about a day, now it just takes a couple hours.