I'va almost always watered about a quart of fresh water per 3 gallons of soil, wait a few minutes, then feed to slight trickle of run-off. A couple of cups total. Works good with my schedule and nutes. I use Fox Farms, which is known for it's salt build-up, so I do monthly mini-flushes anyway. (followed by a dose of humic acid to the soil)

I pack the soil in the bottom 1/2 inch or so. A little escapes over time, but not a big deal. A tablespoon total, if that. Was using duct-tape to cover the holes in the sides of my 5 gallon buckets, but it's unnecessary. The roots hold the soil in, soon enough. Been doing it for IDK...6 months or so?

I was using that shade cloth (without interior rocks, to keep the soil in) for quite a while. But roots grow thru it, and I hated having to rip 'em off for transplanting. Tried leaving the shade cloth intact for transplant, but she runted-out. (smallest plant in the room)

Depends on the size of the holes, and the chunky-ness of the soil, too.