I got it. While taking our 350 in for service, I sat with the service manager who was nice enough to spend time explaining the banjo fitting and how the 2 crush washers situate on the gx470 and he even gave me a way to temporarily plug a brake line while disconnected.
So I spent some time cleaning that fitting and after some brushing with pb blaster, the original washer, which was fused, flattened, and scored, came off. I think that was the culprit as I have a clean new one there now with no leaks for the last 45 minutes of test driving.
Time for a brake dance.
And I learned how to get fused rotors off of a gx470 this week, so I've got that going for me