Lastly, in order to replace the white 90 degree elbow with the part that Midnightsun recommends, would I need a PEX expander flairing tool to do that???
Nope, no need to flare but I would not try this in freezing temps. This should help.
I am not 100% sure on how the seal is made at the pump though. Pretty sure it will work but not 100% sure.