Darren
Talked to my son again about the abs system and he dosen't think that is the problem as you would know when that comes on.
Lets walk thru this again.
Low brake pressure to one front wheel. Why?
Restriction in brake line? where? In steel brake line? Did it get pinched when you were making repairs? It could be pinched off enough to allow a bit of brake fluid through to apply the brakes and bleed the brakes but not as much as the other side causing an imbalance, therefore low braking pressure.
In flexible brake line? Same symptoms as steel line above.
Are calipers operating properly? Does piston expand and retract easily? Do calipers slide freely on mounting bolts? Have calipers been rebuilt? Have calipers been replaced? Has both sides been replaced or rebuilt or just one side?
My son says that when doing major brake work he would always install new or factory rebuilt calipers. If one flexible hose needed replacing, replace them both. Be sure the calipers are free on their mounting so they can work the way they were designed to.
If I think of anything else Darren I'll put up another post.

Cheers

Don