If you increase your inverter size, you most likely need to increase the fuse protection in the circuit along with possibly changing wires to a larger size wire to handle the load. I say "likely and possibly" because we don't know what you have. To tie a standalone inverter into the the WFCO to send AC voltage to all the outlets when on battery power you need a transfer switch or some sort of switching relay. That is an inverter/charger in the picture, not a stand alone inverter.
Here is a link that explains sizing fuses and wires for an inverter circuit. Click on the orange download button in the upper right corner.
... discovered that there was no dump station ... and walk it to the nearby toilet for disposal. Emptying the Cassette initially and then making 2-3 trips with Gray Water ...
Have to wonder if they didn't have a dump station because their septic or holding tank was not adequate for that purpose. Best practice would be to ask for permission before dumping a cassette into any public toilet (flush or pit).
Thanks @webers3, that meter looks similar to the one I have but simpler. I'll take a close look at mine to see if perhaps the impeller is slightly jammed with debris. Someone leaving a comment about yours noted that his impeller was slightly blocked and its accuracy was affected.
@Gomers2, the owner's manual doesn't specify tank capacity. I understand that it's 25 gallons only because that's what nuCamp's web information lists for the 400. You're right, the level indicators are really vague and can't be used to determine when a tank is full. I guess that a dependable flow meter may be the best guide.
@Gomers2 I made the comment about the possibility of "8 amps" from a 100 watt panel. I did say "on a mythical perfect day in the lab". Which is hard to duplicate! I did see 7 amps on a couple of occasions on great days in mid summer in the desert.
In the winter, I was happy to see 3 or 4 amps from that 100 watt panel.