Good write up. It was especially good for me as I have a NL 10 2 CDSE so a lot of things you did on yours I can do on mine also. I have the caps to disconnect the outside shower but when I removed my seat bottom on the dinette there is no way I could reach my outside shower. Then I discovered that I can reach it from the dump valve compartment. When it warms up a little I'll be doing that. Also I added some hard foam to the dump value door. Then I leave the light on in the compartment as mine is the same as yours, all LED except that light in the valve compartment.
We were in Branson in last month when the storm hit there and we dropped to about 5* and we were comfortable in the camper. I have a 2 remote sensors on my weather station so I had one under the wing of my camper for outside temps and the other one I put in the dump valve area. I never seen the dump valve area drop below 40*. We used everything in the camper as I filled the tank when we arrived and then disconnected the hose and we just used the fresh water tank for our needs.
Another thing I have to work on is keeping it from getting wet under the mattress. I noticed even when we where in Alaska when we had a few cooler days that it ended up getting damp under it. I'm looking into the use of hypervent under it but another fellow on another site suggested I look at something called Cedar Breather. It looks like the same stuff except the price is much better on the Cedar Breather. For Hypervent for enough to do under my queen bed is right at $130 for the 10 linear feet it would take to do it. The Cedar Breather is $150 for it but it also is 39" wide the same as Hypervent but it is 61.5' long. I'm thinking if a person could get 4 or 5 people to go together and by a roll together then it would work out to be about 40 to 50 dollars each plus shipping.
I had also made up a hard foam piece to fit in the outside shower compartment and this seemed to work out. The power cord outlet is a problem area. When you have the power cord out you have an opening there that really has no protection. I used some more hard foam and cut it to fit the door opening with a very small opening for the cord to fit out. I would like to convert my camper to an external connection for the power cord and do away with that box as there is absolutely no insulation factor on the inside of that box the cord wraps up in. That is the big black box in the photos under the dinette. It is a single layer of plastic. I'm trying to figure out a way to insulate it as it has to be a big cold air entrance.
I agree the city water connection is terrible. When you look at it from the inside if it is light outside you can see how thin of a piece of plastic it is. I think on it I'm going to try the expanding foam around it to get some protection in this area.
I did have the fresh water drain freeze up a little. When we got ready to leave I wanted to empty my tank but no go. So I borrowed my wife's hair dryer and it a couple of minutes it was thawed out and I could drain my tank. I need to figure out a way to keep the drain from freezing. I'm looking for suggestions for this.
Sorry for being so long winded but I really like working on these things to make them better than what came from the factory and I like sharing what I have done to mine.