This doesn't address any of the three questions you asked, but there are other factors you should consider in comparing the 16' and the 17'.
The 16' has no screen door, so you can't leave the door open for ventilation. This is because the door on the 16' curves to match the hull of the trailer. That curvature can cause leakage problems in older trailers.
The 16' has a 2 cu ft refrigerator
versus 4.5 cu ft in the 17'.
The tanks in the 16' are (I think) smaller than in the 17'. Some older 16' Casitas don't have a gray water tank.
ON EDIT: the 17' has a full 54" wide bed in back. I think the 16' has a 48" wide bed. That accounts for half of the extra foot.
Others may be able to address your specific questions.