One thing I've speculated about Ed is that he could've used a pulsed radio signal to vibrate the lattice structure of the coral rock and eventually reverse the polarity of the rocks.
The flywheel, when spun at a certain RPM, generated a specific frequency based on the RPM. Ed most likely speculated that based on the size of the rock he wanted to lift, he would need to adjust the frequency. A smaller piece would require a higher frequency and a bigger piece would require a lower frequency or vice versa. Would need to do more experimentation if this hypothesis is correct.
Maybe one of Ed's relatives or family members was an electrical engineer or collected various kinds of radios at the time, and gave them to Ed or maybe Ed himself collected them. When he made the flywheel, he most likely took apart the radios and reassembled them in a certain way were he could use energy from the flywheel in junction with the radio parts. He most likely experimented with different combinations of parts and different frequencies to manipulate energy in the lattice structure and the whole of the rock, and eventually vibrating the whole lattice to the point where the poles reversed. He must've had somewhere to 'break' the frequency and let the rock drop after he moved it around.
Another reason why Ed worked at night because of the various amounts of frequencies coming from the planets, the moon, and other stars. He had a lot of time at night where he could observe the positions of the different celestial bodies. The frequencies of them could've played a role during the night, and he probably knew how to do it during the day as well but was too worried about people discovering his secret.
Ed also has various pools of water around his property. During the night, the water would absorb the frequencies from other stars and the wheel's frequencies could also transform the water in some way.
This is all speculation; I would like your feedback on this theory