The only way the disconnect terminal part # DW05312 that you referenced would cause electrical problems would be if it wasn't properly connecting to the battery it was installed on. Other than that it wouldn't be any different than a standard battery terminal. view full answer...
The correct fuse bypass to use on a 2016 Chevy Sonic is the part # RM76511. I attached an install video that shows the kit being installed in a similar 2016 Chevy Sonic as yours as well. Since you do not have keyless entry the correct fuse to bypass is the DLIS FUSE 1 like you mentioned. view full answer...
It sounds like you either have a Sensor # T21301VP that has gone bad or more likely there is some debris stuck on the sensor that is making it think it is full. I recommend taking a Valterra Spinning Master Blaster Tank Wand # VAL88VJ and using it to clean out your black tank. This wand has a spinning tip that allows it to spray water all around the tank and can help to clear debris stuck on the sensors and walls of your tank. view full answer...