Hi,
The 225F appears to be submersible, correct?
I would simply place the pump inside the sump and then feed the c02 output into the existing mag drive for distribution to the tank.. Just use some flex tube from the NW pump and stick the other end into the sponge that (should) cover the mag intake....no need to hard plumb it for a test...
That seems quickest and easiest...You can leave the c02 outlet just feeding the overall sump water, and let the mag do it's thing, but that will waste some c02 for sure. I have done this for my 180 when I had a sump and it works well. Tom does similar iirc.
The extra time in the lines will help dissolve more of the c02 and the water will be 'clearer''.
Does this make sense?