We have only slightly larger black and gray tanks and two of us can go 7-10 days.
Fresh water and propane should not be an issue at all.
Depending on size of batteries, and your personal power useage, three days is doable. (We can go three days on 2 12v batteries.) Your led lights will help a lot with that. If we run the generator during times like that, its usually shortly after we get up while we're running the furnace to take the edge off and running the pump for brushing teeth, morning bathroom chores and maybe cooking breakfast. In other words, a half hour of generator during the time you're using the most power will also go a long way toward conserving batteries.
PS In this same section, it might be interesting for you to read the thread on "how long can you dry camp?". :)
But, your mileage WILL vary. Everyone's personal habits and useage will vary. But this will be a good " test" for you. Enjoy!!