Hydro water fill level with perlite Q

I'm planning a 2x2 sCrog laundry sink grow. The sink will have 4 smartpots filled with perlite. I would then have a 5 gal bucket with airstone and nutes mixed in a seperate cold room which I would pour into the sink allowing them to soak for 15 minutes and then drain underneath into a waste bucket.

1)Should I fill til 25% of the pot? or like 75%? or neither. I am currently doing hempy buckets but I top feed only.
2)Should I have any other concerns based on these perameters? Light/heat/smell are not an issue.
3) Is drain to waste going to be the best method for this? Or should I just re-use the same nuted water for 7 days and then clean the bucket and mix fresh nutes? If I re-used it I would check the ppm/ph and add nutes/water as needed.
I realize i could make this simplier with a water pump, but it might be a couple months for that, I already have all these supplies 100% and plants ready to go in.
4)If the sink only takes 2 minutes to drain should I allow a longer soak? like 30 minutes max right?. I don't have a problem watering every ~3 hours but I don't want them to dry out, but if they do soak for 30 minutes, what is the BEST amount of time to wait until the next water?

Thanks in advance.

*if picture confused anyone its a 25 inch deep sink, so 10 inches for the pot then the screen is 10 inches above the top of the pot. this way I will have 5 inches in between the screen and my 2x2 T5HO which will be hanging right above the top of the sink at 26''. When they fill the screen I will switch to 12/12.Also I plan on cuttin a hole right above the top of the pot so I can water through the side and trim bottom growth, and a fan will be hitting in the hole.

Well, no expert here. but I am exploring perlite, after, clay pellets, Wonder stone, and SuretoGrow (not).

Perlite has some properties to exploit. That is how I see these media. All have different properties.

Perlite is great for wicking up the water. So, an idea I've been trying is to take a container and putting a hole in in it about an inch up from the bottom, and no holes in the bottom.

So, I'm not sure what soaking is for? But, I love the idea of the bathroom sink grow. I am going to treat this in a much more simple fashion. With the hole an inch up. I water every 4 days or so. The water at the bottom just wicks up over a few days.

And I just make up a solution in container, and over-pour in, to rinse out the old salts and let it run out the hole. Done.

I would go with 75% full.

I have a dozen pumps of all sizes that I have tried with various failures. I don't think it is worth it to re-use. You only know the proportions of fresh. After the girls feed, you won't know the proportions of the run-off, i,e. Drain to waste.

I just set some clones on a 1/5 Clonex wet, perlite. I leave rock wool cube on top and just slightly set into the perlite so it doesn't move. I want that cube to dry out on all sides and roots grow down to get water.

It works. Btw, another thing I do now, is let that clone get a bit root bound in the dixy cup before I transplant it into a slightly larger container, let that get root bound again before it goes into the final grow container.

It works.