Need Help getting Flow rate correct

Hello Everyone. I have grown once with this set up, and the results where ok. Ide say it was my lack of knowledge that effected my quality yield and over all health of my plants, but I must say I learned a ton from my mistakes and from reading this site.
So from what I have learned and with you'll help I except my 2nd time to be even better.
My issue I would like to resolve is that I cant get my system setup correctly so that I get decent pressure coming in to my buckets without draining my reservoir.
If you take a look at my picture.(the res was seperated in the pics becuase I was moving it around but i think you can see how it looks when together) The Green arrows are the water coming from the res via the 250 gph submersible pump, up the tubing and entering each grow bucket from the top. Then the blue lines are the water coming from the bottom of the grow buckets thru each bucket back to the res. All lines are 3/4. If you also notice in the pic I have a shut off valve between the submersible pump and the buckets. That was used to control the flow coming from the pump. I basically was choking the submersible pump in order not to drain the res. And as you can imagine with the shut off valve the flow coming in the grow buckets was minimal.
Now I did diy this system so be gentle...... lol. I did put alot of time and thought into the build
Ide like to try to use the same set up I have with a tweek to get it right. If possible at all Ide like to work with the pieces I have. After each little piece the system added up in price especially the Black 3/4 hose.
Like i said before i ran the system for nearly 3months as is. but not like I had intended it to be.
The res is a 10 gallon and the reason I choose this container is because my thinking was that Since the system was self leveling. I needed to figure out a way to keep the right level of water in the grow buckets while still increasing the volume of water in the res. So if I use a container thats about the right height but holds more volume.
I dont know.. you guys are the ones who know. I feel like I am over thinking this..... Help. me out please and thank you

ok so I was thinking about solutions that would let me use the pieces I have and with a small investment, I can make some changes.
This is what I am thinking, instead of letting the water just flow into the grow buckets from the submersible pump I can attach some micro spray nozzles in the buckets via 1/4 lines. My thinking is I can run the submersible pump and the spray will fill the buckets but at a slower rate allowing for gravity to flow from the bucket back to res without emptying the res. I am thinking itll add air and movement and hit the roots that are in the hydroton.
Thoughts?

So your buckets are filling up faster then they are draining? If I'm understanding you correctly, maybe larger return tubing would help.

bigger return lines, or bigger reservoir

Thanks guys for the advise. What I ended up doing was changing the size of the lines coming out of the submersible.
Orginally all the lines were 3/4 I ended up changing the feed lines from the submersible to half thier original size of 3/4 down to 3/8. so basically taking half the volume then originally.
The system has been running for about 2 hours now and the reservoir has not emptied and there is water about 3 to 4 inches above the submersible. So I am gonna give this set up a try and see how it works.
side note.... I am sure I was mixing my nutrients wrong. If you look down to the pic you will see what I call a nutrient turd in the lines of the system. They where completely cover the inside walls of all the lines.
The sytem is running now with just a light amount of bleach to kill and clean eveything.
In the next few days I will vaccum all the water out and clean everything up and start the grow.