How to mount sdcard1 (external SD) as internal storage?
Due to how Android handles SD card permissions, it is no longer possible to "swap" the internal and external storage of the device and trick it to use the SD card as "internal" storage any more.

Since you are rooted, I would look into any of several Android 6 based ROMs that are available for the Moto G, after installing one of those you can adopt the the SD card as internal storage. Be aware that this will make the card unreadable in other devices without reformatting it and it can only be seen via a USB connection since it will be formatted as ext4 and encrypted. I would recommend using XDA's Moto G forum area for more information regarding specific ROMs and how to flash them. 

The other option would be to use an application like Link2SD, which would require you to partition and reformat your SD card, and it uses symbolic links to the partition on the SD card. This still requires the app be installed on the device first and moved, but it can free up significant space and using the paid version can move even more data to the SD card. See the application linked above for more information.