Thank you Sharon is SAM and Binghi! I made what is likely a typical noob assumption that the pump is needed to move water through the water lines, no matter whether the source is the fresh water tank or city water. Having disconnected city water and set the Nautilus to dry camping mode, I find that the pump works perfectly as it should. I'm set for the moment until I encounter the next noob situation.
I'm with you on the suspension, rubber torsion axles are probably the worst for going down rough roads. The Dexter specs list a whopping 1.5" of up travel for an axle at load capacity. One of the hurdles when replacing the axle is that the tube serves as a cross member so you can't just remove it. Either build a replacement cross member or pull the swing arms out of the tube. Leaf springs aren't necessarily bad if they are designed for a good ride (long mono leafs or similar) but the typical trailer leaf springs aren't gonna cut it. I've been toying with the idea of coil overs which are pretty compact but do need a way of locating the axle with trailing arms or similar. Maybe next winter I'll brush up on my non-existing welding skills ....
Leaf springs would be my last choice. I’m surprised it was that bouncy. After having owned a tent trailer with leaf springs towing the 400 is a dream. The more overland-ready campers use coil springs and shocks but I have no idea if that could even be retrofitted.