First of all I would like to say well done. You have made a very professional looking job of it

Secondly, I may be wrong but the angle of your pump doesn't look flush?
Try and keep it as straight as you can as you could put strain on the motor brushes which could result in your pump wearing out quicker.
I was told that these pumps will prime up to 3 feet. Maybe try and keep your pump lower down and closer to the outlet.
Cheers
Matthew