I have come to a conclusion that I need more suggestions than most posted threads that have similar issues. I am past the basic tests, but I am sure there are more options.
The issue: I cannot install any new APK's either from Google Play or even via ADB. I am getting the common "Insufficient storage available" error. I assume all installed files land in /data/app first which is on the internal storage. So I have attached some screenshots below that prove that everything should be working fine given there is a lot of free space left.
Also, other things I have done are:
- Wipe dalvik cache and /cache
- Fix Root permissions
- copy /system/xbin/busybox to /system/bin (cannot update busybox since I cannot install or overwrite due to this error)
- Check both /storage/sdcard0 and /storage/sdcard1 have enough space.