First off your Fluval is not producing anywhere close to what the box or the manual says. Those numbers are usually made up by the manufacturer and in real life are much lower. Different reasons for that. Have been discussed before, do a search if you really need to know them.
The picture of that reactor:
1. How is degassing handled?
Every external reactor accumulates gasses that do not disolve in the water. Is there a particular way to degass this canister automatically, as it runs?
2. The check valve is connected to a nipple by just slipping the air tubing over the nipple.
That's a huge risk. If the small hose comes loose the water will shoot out of the nipple very fast and very far.
3. I think I see a pH probe on the side.
This is for people that like gadgets. No real need for it if you are not into gadgets.
4. Not every pump will have a round electric cord. Unless the metal tight fit connection on top somehow seals perfectly around any cable please be aware that you may find a pump with a round cable.
5. Two 90 degree elbows - reduce the flow quite a lot.
And to answer your original question - How to put a pump in a sealed canister - This is the fitting that you need: http://www.go2marine.com/product.do?no=92459F
Keep in mind they come in different sizes. You need to match the size of your cable (diameter) the size of the fitting. There is a rubber part inside that fitting that tightens around the cable. The contact cable/rubber part needs to be as tight as possible even before tightening the fitting.