Wow, with that big new pump you have, you still can't get the overflow running wide open ... this is good as you will not have to ever worry about your overflow being overwhelmed
Nothing wrong with that
As we discussed with Grizz, you only need 6 or 7 times sump turn-over/hour
No point in running a larger pump for now. Get the system running and worry about it later
I know, you don't like the gate being so 'closed-off'
I agree with your concern about it plugging up, but that can't happen if you cover the top of your overflow with a sheet of acrylic
Only the snails that grow in the box ... the ones that went through the teeth ... will ever get big enough to plug up the gate
Plus, the velocity of water passing through such a small opening will most likely keep it clear
You can also, once a month or whenever, open the gate full blast and flush it out
I found a snail in my chaeto drain this way ... popped right out
I'll sit back now while you keep adding pics .....