Should returns push toward the overflow?

Powerheads are not the answer. I have just 2 EVO 1400 in my 90gal & I only have them on 10 hours a day. During my night mode as does nature, seas are calmer & my fish will rest a whole lot better than getting bounced around.

Matter of fact I haven't ran them in a week, because my battery in my battery backup failed & my replacement battery will be here tomorrow.

My valve on my return is at 1 o'clock opening. If I have it open all the way I will have RAPIDS in my tank & my pump is in my basement.

That said, you want to disperse your return water. After that you can have your powerheads move all the water it wants. If dispersing is not happening, then you will never get all or will take a LONG time to get what you have dosed, WC or treated water overall.