You can save them as is to your computer in a folder and just use them on the one device, with DRM intact. Save the books from amazon and use the transfer via USB button.
Removing the DRM really isn't that difficult with the right programs, but we aren't at liberty to speak of them on the public forum.
I'm sure the how-to on stripping DRM isn't supposed to be discussed here but isn't that hard to find out. It ain't rocket science. As far as saving to your computer, I save all mine to my computer (with or without DMR, it doesn't matter) so they will be backed up. I have an automatic backup which everyone should. I let mine lapse for a short time and it caused me no END of problems.