I will add one gripe:
The camper carries 22 gallons of water but there's quite poor access to the liquid. The sink pump drains battery and cannot fill a large container in the sink. The outlet on the rear of the Grandby when opened full drains maybe 1/2 gallon a minute. !!
Wow, that doesn't sound right. The pump should not drain the battery filling a 'large' container. Is the battery in good shape and fully charged? Do you have solar or charging from the truck?
I am not sure what the issue is, but you should be able to use the pump extensively, along with lights and other devices for at least a day or so without running your battery down.