I think there is a way to get articles on your kindle. I think you can use the send to Kindle feature.
As per apps and stuff, you would need to jailbreak your kindle. Then you can do more with it.
Here is the link to the jailbreak thread.
https://www.mobileread.com/forums/sho...d.php?t=275877
For pdfs to render better, I think you need to jailbreak and add Koreader.
Calibre I am not sure but someone should be along shortly with more answers.