Try angling the eyeball so it breaks the water surface but keep the 45 deg angle, it might help. Right now the current is completely underwater and that is what is creating the whirlpool effect. it seems that either you have a very small diameter opening in the eyeball or you have a very oversizes pump and the water is shooting through the filter at a very high speed. As a thought you don't have your multiport valve on recirculate instead of filter, do you?

If you decide to change the eyeball for one with a larger opening usually you just have to unscrew the retaining ring to take out the old one and put in the new on. No draining is necessary. You don't have to change out the entire fitting, just the actual eyeball part. A larger opening will allow more water to pass and it will not come out as fast.
Same idea of a nozzle on a garden hose. When the nozzle is on the water shoots out very fast and hard because it is going through a small hole. Take off the nozzle and the same amount of water is coming out of the hose but through a much larger hole so it does not shoot out as fast or as far.