Yes, rusted spring bolts and anything else thats attached to our cars are a constant up here. With all the Salt and Sand we use on the roads in the winter, its a surprise some cars are still able to stay together.
If/when you go to replace these springs, I would say not to get used ones, and don't re-arch these ones. Either of those options are just temp fixes. Look into stock replacements if you want stock height, or full leaf packs if you want to lift a bit. Or put together a bastard pack using as new a main leaf as you can find, and making sure the next leaf under it is nearly as long or just as long as the main leaf so you don't get that negative arch in it like yours is right now.