I would try the back flush method. A 2 inch trash pump won't create much pressure in a six inch pipe with low gradients.
Ditto
They have the rubber reducers that hold on to the pipe with a hose clamp. I'll bet you could regulate the pressure that the pipe can hold by how tight you make the hose clamp. Too much pressure and the reducer blows off the pipe.....
I'd feel better about having a pressure gauge on it somewhere though.
I'd take the well screen off of the other end of the pipe before back flushing.
