Nice little FGRV. It looks as though you have a solution to the migrating cushions. Here's another idea. I was told to keep the table in the down (bed) position while towing. When in that position all the cushions fit in the bed space in a jigsaw puzzle style. The cushions are not going anywhere! (See my photo)
Since we camp in cold to hot temperatures I had to come up with a flexible and easy bedding system which is described in further detail in other postings of mine. Basically, I have several light
to mid-weight queen-size (or any size of your choice) comforters that are easily attached to one another with a button/loop system. One comforter has buttons spaced about 12" apart. The other comforters each have loops spaced the same way. This way you can loop and button several comforters together. This system is even easy to use in the dark. Velcro or zippers would be noisy and cumbersome to use. In cold weather we like to have the flannel side of a comforter next to our body assuming you have a flannel-sided comforter. You can get very inexpensive, yet plain, comforters from IKEA. Glamper side note: Each side of our comforters have a different print, solid, stripe or plaid. As a result, when the bed is made up we can choose from a variety of designs to be uppermost. This feature is not essential but is fun!
In addition, wear a knit beanie hat, socks and anything else to keep you warm. You might want to tuck in a heated hot water bottle before going to bed. I like to put my clothing for the next day in a drawstring bag or empty pillowcase at my feet in bed at night. In the morning I can stay in my warm bed to put on my (relatively) warm clothes.
My photos also show the custom made mattress pad topper that I made in two long pieces so they are easy to store in the benches. Look at #4 posting here: Memory Foam
We set the heater at a relatively cool temperature so it only goes on at night if it gets really cold. The noise wakes us up however. This is probably a good thing since we can be aware of preventing fire and we can bundle up more. We sometimes just heat the space before heading to bed and upon rising.
In any case, you'll find your own way to stay warm and to control those cushions. As to how to tune out noise of bullets, I'll let someone else answer that issue.