Your big mistake is relying on quicksave and autosaves.
The game only maintains one or too of each and each time it saves it overwrites one. They're also more likely to become corrupted.
You can always open up the console and use the COC command, but you'd need the location codes.
Alternatively, I'm assuming TLC (No clipping/fly mode) still works. Hit console as soon as you load and type it in., move back onto the rock and then type TLC again.
No doubt, but alas, actual saving is far too time consuming an endeavor to undertake. If only it weren't so. Anyhow, cheers for the help. I TCLed my way to safety and popped off the baddies. There was one side affect, however. As I was leveling my aim on the soon-to-be-head-shot mutants across the river, I suddenly saw a vicious bobbing blod pass across the bottom of my sniper sights. Loyal to the end, Dogmeat had apparently seen my imminent plummet into the river below and dove in to rescue me. Unfortunately for him, I don't think his dog paws are equipped for dragging himself back out, and so will soon be turned to an irradiated blob of dog soup. On the plus side, he served as a distraction for the bemused mutants, who just followed him perplexedly with their miniguns without opening fire until I broke the reverie by exploding one of their heads in a fine bloody mist. If you don't make it through this one, RIP Dogmeat, you met a fitting end.