Snowman9000 - Did you ever figure out how to unfasten (<-is that a word?) the carpet from that slanted piece? My unit has been in storage since you posted your comments, so I cannot look at mine to come up with suggestions. My first thought would be to drill a larger hole to allow a fish tape to be routed across and then pull a new wire. Except ????? I would not know where to route that wire.
The other thing I would check is whether the sensor wires leaving the fresh tank might disappear under the coach body over across the walking aisle and then up inside the wall to the Level Monitor. I say that since the monitor panel on mine also has the propane level and the battery charge level that are also on that side of the RV body. Just thinking they may have clustered them in a run to the other side. Well, I just checked on your floor plan and it is so much different than mine that this paragraph likely would not apply to your unit.