Maybe add this to your reading list....
https://www.pentaxforums.com/forums/169-pentax-full-frame/335318-k1-owners-im...ml#post3847865
Since getting a K-1 I've decided Pixel Shift is a frill type option of dubious value. Sometimes it gives you something, sometimes it doesn't, but it always takes time. I got the GPS in my K-1 and love it, but it's not essential.
My wife is still using her K-5 and has no plans to upgrade... the K-5 has more dynamic range than a K-3. If you do a lot of sunsets, that's nice to have, but not essential.
The main thing with the K-3 is buffer size, burst mode, and AF. I shoot a lot of small birds and I find no practical difference in AF between the K-1 and K-3, if anything the K-1 is bit slower. Working with the K-1 in the blind trying for bird shots, I feel like I've gone back to the last century. It's not an action camera.
Tha main advatage to the K-3 is magnification because of the pixel size, for macros, it makes your macro lens even more macro, for wildlife, it makes your long lens even longer. A real money saver in that sense, as reach is always expensive, and anything you can do to augment the lens is money saved.
There are many images where I get better images with the K-3 with than with the K-1 and the same lens. Especially when I have to crop the K-3 image like 15% and the K-1 image 65%. At that point the IQ is in favour of the K-3.
I'd seriously look at a K-70 in your position. Apart from the non-conforming battery issue, it looks like it could be the best APS-c body out there at the moment.