Okay could be your drums are over adjusted. Did you replace them all? It’s possible to put the Limoges and springs in the drums on wrong and rather than hold them away they pull them into the drum. Double check the drums as poorly adjust can feel ‘okay’ but give a weird pedal.
Is the mc he right one for your callipers? They are different. Deffo set the rod as per the factory guide. It’s fairy important lol, I still think it sounds like the rod is over adjusted and bringing the brakes on ‘too soon’.
You can stick a ball of blue tack on the end of the rod then actuate the pedal and then look at the blue tack to get approx clearance - I can’t remember what it should be but it’s in the book. I can look later
Have you plumbed the g valve the right way? It’s not a part that fails.
The brake system on a defender is simple, it won’t be anything ridiculous, Just needs methodical approach to go through it all.