Lots of tips on how to move apps to sd card: http://www.pcadvisor.co.uk/how-to/google-android/move-data-from-android-phone-sd-card-s7-3466195/
Another guide on how to push the "Move to SD" button in the app manager. When I try it most of the time I get "Cannot move app." : http://www.tomsguide.com/us/move-android-apps-to-sd-card,news-21279.html
Can you change a setting to make apps always install to sd? Nope, even though there is a setting that says it does that. Here is an extremely technical post on how to try to get around that: http://www.fixedbyvonnie.com/2014/06/install-android-apps-sd-card-default/#.V9ihGcT3bCQ
This one is a far more succint post that covers the same solution as Vonnie's post: http://www.baatkar.com/2015/12/how-to-install-apps-directly-into-your.html
This explains why I couldn't find the Enable USB option and the new secret way to find it:
http://www.technewscentral.co.uk/how-to-enable-usb-debugging-and-developer-options-in-android-4-2-and-higher-android-4-2android-4-3android-4-4/id_7250
Here's an ad for a Windows program called "Android Transfer" which is supposed to make it possible to transfer apps to SD card when you are otherwise blocked. It seems to use the USB debug option to manipulate files on the Android directly: https://www.recovery-android.com/install-apps-on-sd-card.html
This shows how transferring apps works for 6.0. I have 4.0. It's less nice for me:
http://www.howtogeek.com/114667/how-to-install-android-apps-to-the-sd-card-by-default-move-almost-any-app-to-the-sd-card/
A possible hint about clearing the cache: http://www.pcadvisor.co.uk/how-to/google-android/how-fix-androids-insufficient-storage-available-error-message-summary-cache-3623467/
Best guide so far about enabling USB debugging and then installing the android debug app on a PC and using it, but the page is filled with javascript ads making it hard to view on PC: http://techgage.com/article/moving_your_non-movable_android_apps_to_an_sd_card/
Getting java error does not belong to 2000. Here's a Google search and several links of people trying to figure out how to get around the "java error does not belong to 2000 problem:
https://www.google.com/?gws_rd=ssl#q=error+java.lang.securityexception+package+android+does+not+belong+to+2000
Hair-tearing about the does not belong to 2000 problem in the comments of this hint: https://disqus.com/home/discussion/fixedbyvonnie/how_to_install_android_apps_to_your_sd_card_by_default/newest/
An answer which involves being super user. This won't work unless your phone is already rooted though: http://stackoverflow.com/questions/28681057/exception-package-android-does-not-belong-to-2000
