I guess I’m confused why you think you need the second pump. A pondless is a simple circulating water feature - pump in the reservoir pumps water to the top where it flows back down to the reservoir. The reservoir itself is filled with the blocks and topped with stone to conceal the blocks.
And technically any rocks are “good enough” - it’s more of an aesthetic concern. What type of rock are you showing us? Are they soft or porous? Sharp rocks aren’t a great choice either. Personally I wouldn’t use those rocks, but it’s not my yard!
The idea was to have the waterfall split in two. One direction would descend down to the lowest point to the left, where the pump is located. The second direction would flow to the right. However, how can I have the water go towards the right, when the pump is to the left? (I hope this makes sense)
I don't know very much about rocks to be honest. I dug those up while planting trees in my yard. I've seen them called "Baja Cresta" rocks (at least they look identical). I don't know how soft or porous they are.
When you say you wouldn't use those rocks, for what reason? The color? Size? Shape?
I really appreciate your input. I need all the advice I can get!