As far as the pump vibrating; I have seen folks use silicone baking mats (Pyramid Pad on Amazon, roughly 5 bucks) to put under pump to dampen the vibration. Might be worth a shot.
Good advice with the siphon breaks, my returns sit about 1.5" under the water currently, but I may move the loc lines to set up current or hit dead spots as I see fit in the future. I drilled siphon breaks just in case the returns and am glad I did (although I had to reduce the flow of my drains so that the water level in my overflow was higher, else it sounded like someone was peeing into the water 24/7 )
I may have missed it in the thread but what it your proposed stocking?