Susan with the exception of your floor issue pretty well every thing else is pretty easy to fix and pretty standard maintenance issues.
The floor is going to be your biggest problem depend a lot of how rotten it is. If you pock it with a screw driver is it really spongy or is it just the top layer of chip board that is peeling up?
You can get the new curtain holder at pretty well any drape shop or hardware store or perhaps even Walmart. Just drill out the old rivets and replace.
You can buy replacement parts for the door at the Scamp
online parts store for $5.
You can purchase rivets and a gun at most hardware stores. But Scamp does sell packages of all the sizes of rivets they use on the trailer along with all the different sized cap holders and caps you will ever need. Otherwise you can also buy the caps and cap holders from most major hardware stores. As far as what size rivets you will need do a google on this forum and you will find a thread that I seem to think is called Scamp Rivet Sizes or something like that.
What do you think you are missing on your jack to keep it in place? From the photo it looks to pretty standard. There is a round bar that can be used by putting it in the holes to jack it up a little more but you dont need that to keep them in place. Scamp also sells the bar online.
Eddie is right again about the hot water tank. It may be that some not so great water was left in it. Simple needs to be cleaned out. Sometimes sludge will build up in the bottom of the tank as well. You can purchase a water heater rinsing wand
from Camping world that helps with that in the future. If giving all your tanks a good cleaning out with a little bit of bleach (google the forum for how to do that correctly) doesnt clear the problem up it may be that the you need to replace the anode rod in the hot water tank but more often than not the tank just needs a good cleaning.