Amazingly, from what I can determine, your SSQA lever assembly is less beefy that the one on my DK-40 series Kioti. That is wierd, if true, because of the larger loader, attachments, etc. you use on the NX Series machine.
And I've had the exact same problem of the lever being tripped, though not to the point of releasing it's implement, fortunately. I think you'd be better served using the next larger size expanded metal on your grapple, and on your brushbar, if you have one, as I have done on both my grapple and brushbar; so far, nothing has gotten past either.
Sometimes I have the loader and whatever attachment lifted fully, essentially over my head, where if anything were to release, it could be a deadly outcome. Initially I used one of your favorite in field repairs, a bungee cord, then switched to a looped section of rope that I wind around the crossbar support and make hold the handle in fully closed position. I've also made up small signs to place on the crossbar of my grapple, bucket, tree shear, to remind me to ALWAYS close and secure the SSQA handle. This I did because I realized I'd lifted my log grapple over my head one time recently, and had not locked the lever. Scared me pooless thinking about what could have occurred.
It only takes once for a very bad outcome. I agree 100% that the SSQA lock/release lever is virtually unable to be seen from the tractor seat, probably more so in a cabbed model.
BTW, I like your strap and clip for the handle on the SSQA, though it might cause some issues getting it undone in frigid temps.
Fittings wise I have what came on the Kioti, mostly metal tubing with NPT, and then hoses with JIC, I believe. Each has it's benefits/flaws. IMHO. Things will get broken no matter what one chooses, that's just the way things go when working machines and getting things done.