So here's another question. Let's say I get an R-Pod 172. Dry weight 2,128lb/hitch 244lb. It probably is going to be 3100lb/380lb-ish loaded with options/cargo/propane/bettery (just guessing here). Do I want to add a 100lb WDH? It is going to be way over my capacity of 425lb (or GVWR of 5,400lb), but I know it is going to distribute some weight to the trailer. I just think it still is going to be heavier than not having an WDH. I am still trying to figure out how it works.... any input is appreciated.
Sooner or later you will want a bigger truck/tow vehicle. Maybe now is the time as you are 'splitting hairs' on what works and what does not. And what you can tow with the Xterra might not be what you really want in a trailer. Why purchase what you might not want just because it can be towed by your existing vehicle? Find the RV you want and then get a tow vehicle for it.
For calculations, use 12-14 percent tongue weight including propane, battery, water, all your stuff and the trailer. You might need to distribute that weight within the trailer to get to that tongue percentage. Some weight behind the axle, some in front kind of thing. Scales and especially a tongue scale like the Sherline will help a lot on this.
As far as the need for a WDH, it all depends on how much weight is added to the rear axle of the Xterra and how well it handles it. You many not need any WDH, you may need one. Anderson makes a relatively light WDH with sway feature built in that you might look into.
I think you will be a lot less frustrated if you decide on the RV you want and then acquire the truck or tow vehicle for it.