Re scratching film. I routinely do 6 - 8 sheets of 4x5 at a time, and have done as many as 10, but not unless for a good reason.
I use an 8x10 tray, with 1500cc of HC110.
Unload from holders into a film box, sitting long side across the short side of the box, so the ends are sticking up at the edge of the box, e-up, clipping the corner of the last one, so I can find it in the dark.
Turn the stack over, now the clipped one is on the bottom, e-down. Hold films in the left hand.
Pull films out with the right hand, one at a time, drop into a tray of water the same temp as the developer, pushing down into the water with the little finger, let it "drift" to the bottom, keeping the rest of the hand dry. Go through the stack, the clipped one on the bottom, and herd them all together into a neat stack.
Shuffle constantly for 2 minutes.
When the clipped one is on the bottom, pull out the stack and drain for only a second or two.
Place them, e-down, into the developer and begin shuffling, bottom to top. Rotate 90 degrees clockwise every other shuffle (feel for the corner).
Agitate constantly the whole time.
Pull the stack out together and go to the stop, fix, etc, always using the clipped corner to signify one round.
I use an 8x10 tray for 4x5 with 1000cc developer (you can use 1500 for deeper chem). This was Fred Picker's recommended method for tray development and I have very few problems with uneven development, and maybe only one or two scratches over many years with this. I also do a lot of pan strips, and a sequence of shots is always very closely developed between shots. It's important that the stack is never settled out completely, so they are shifting a bit between each other all the time.
Practice in the light with some of that bad film to develop the feel for it. As others have said, unload all the films into my left hand, holding them at the edges, clipped one on top.