You can always oversize a pump a little and put a tee right after the pump in the reservoir, put a valve on that tee and you can now open that valve just enough to bleed off any extra pressure into the reservoir, could use it as a floom or waterfall to oxygenate.
With 1/2" feeds you may want to run 3/4" from the pump and use 3/4 x 3/4 x 1/2 tees to take off for each site. You can also add a 1/2 inch valve there if you want to be able to equalize flow to each site.
If you didn't already, u might want some elbows on those feed lines, pointed down in the sites. Makes a waterfall and won't blast the bottom of the net pot.
I have made a redesign. I was having problems with water level due to line locations. Going out the main reservoir was too low. Leaked before hitting required water level. Ordered 6 gallon square buckets and will feed down thru the top of the bucket. Not side. Feed will also exit reservoir thru top. I'll post up new photo soon. Waiting on buckets. Water levels now can be controlled by water level in main resy. SHould solve this. Added 800 gpm pump.
Got the water test done. NO leaks. Tested out everything. I have a heater for the water as the weather is getting cool and its in the garage. pH'd the water, added nutes. One more week and seedlings will be ready. Everything is automated. I just need to set a timer to add water to dehumidifier. If I put a small "stir" pump in a 5 gallon bucket timed to refill it daily that'll do it. It uses a full tank a day to stay at 45%. Room temps are controlled by fans as I need some heat from the light to keep temps stable. WIll also switch from MH to HPS. I have a 600/800/1000 switchable ready to go. Took quite a bit of planning but I think Im good. Ill know in the first day or so of the grow.