[Mrmerlin]

For the benefit of the PP trust.

wow sounds like your in deep with this repair.

Here is how I would suggest to fix it the first time.

First order 6 sealing washers,
3 of these will be kept in your ash tray for spares.

Buy a new check valve. since your old one is damaged.

Buy a new hard line,
yes its expensive but its very likely your old one is damaged,
NOTE there is no economy in buying a used hard line,

Buy a new fuel filter.

With your collection of new parts add some PTFE sealant to the new check valve (just a bit) then fit a new sealing washer and screw this into the pump make it tight.

Then assemble the other parts, fit them to the pump holding assembly loosely so the parts can move as needed.

Use anti seize on all of the threads and the B nuts,
fit the other 2 sealing washers and then tighten the cap nut to less than than you tightened the check valve.

What your trying to do with this is not crush the new hard line,

so only use as much force to make the connection tight.

NOTE the sealing washers are one time use,
once you tighten them they are not to be used again.

NOTE using a damaged hard line will result in a leak.

NOTE using used washers will result in a leak.

NOTE using damaged parts will result in a leak.

NOTE to check the hard line simply put a straight edge on the ends of the banjo surfaces,
the faces should be flush from the inside to the outside,
over tightening this part with the capnut crushes the surfaces and moves them out of plane.