I run it at 10 psi.
Less psi does not mean better filtration.
More psi tends to rip cartridge apart.
Canister usually does not leak unless canister gasket is off
Try your local plumbing supply store (box stores do not have them) and ask for 1 micron sediment filter.
Do not get the carbon stuff.
They are about $27.
You could go with disposable type.
They are about $2 on web.
Lookup 1 micron cartridge on Northern brewer site and then search for the brand they are selling.