First of all, stop talking to your daughter about RO membranes. I'm sure she means well, but her advice above is very bad and would ruin the membrane.
Second, please clarify whether you are talking about the filters used before the RO membrane when you discuss filters becoming dirty and needing cleaning, or the RO membrane itself.
I didn't watch the video, so don't know what they say there. However, it seems like they are talking about industrial plants, which are much different in operation than a cruising boat system.
Here is a typical general watermaker component setup: Raw water intake > strainer > filter > watermaker pump > RO membrane > Fresh water tank.
So there are filters and a membrane involved. The membrane is a type of filter, but not really discussed as such in describing components.
Bleach will almost immediately kill a RO membrane. Even a little bit at very low concentrations is harmful. Vinegar won't kill the membrane, but it won't be helpful. Since it freezes at 28F, it would kill the membrane in the winter. Neither should be used in a watermaker system for any purpose.
Fresh water won't foul a RO membrane any more/quicker than salt water. In fact, I suspect less fouling would occur. Fresh water might foul the filters faster if it has a lot more stuff in it than salt water. Often times, this is the case with fresh lake water containing algae, etc.
Cleaning filters is easy, and replacing them as needed is cheap. Carrying around a bunch of filter cartridges is normal for a cruising boat.
Cleaning RO membranes is rare, and few people carry around spare membranes. As long as the membrane is flushed with clean fresh water after each use, fouling doesn't occur much, and neither does calcification.
If the RO membrane does need to be cleaned, one would use sodium hydroxide for biofouling and citric acid for chemical fouling. Again, this is very rarely necessary.
To store RO membranes in freezing weather, just store the entire system in -100F glycol antifreeze like used in protecting boat/rv fresh water systems. This both preserves the membrane and keeps it from freezing. Alternately, you could remove the membrane, put it in a bag with a glycol solution and take it home.
But the very best way to keep a membrane from freezing is to keep the boat containing it in a nice, sunny, warm climate.