The skip I use is to jump on the rocks just to the right of the waterfall (where Mordy’s Secret Stash is) so that I can hop up to that big rock. Then I can use the rock as a shield from the SBA loader and abuse the Unkempt Harold. I usually have to kill all of the loaders that are on the lower level that the stalkers hadn’t killed, or they will push me into the range of the SBA loader. If you don’t go through the Specimen Maintenance area with the stalkers, then fewer loaders will spawn, or they won’t spawn until you get close to the door after killing the SBA loader and you can just run away from them. After killing the SBA loader, you can climb the hill and get to the red chest at Mordy’s other stash, jump down, sell stuff, and jump back over the waterfall again before running to the open door.
I’ve read that jumping over the waterfall may cause the game to glitch and not progress, but it has always worked OK for me.