You're better off sticking with nylon. Any metal has a chance of causing galvanic corrosion.
Most likely... it's being tightened way too much. It does NOT need to super tight. Let the caulk/sealant do it's job. That channel is a great design as it allows for extra sealant.
Get yourself some butyl rubber tape, fill the channel and put a strip around both float surfaces of the external nut and the internal nut. Tighten good-n-snug - but only use a tool to help a little bit. Guaranteed it won't leak and by not going Superman on the nut you won't break it.
Has anyone come up with a better solution then the plastic drain plug system for the offset bracket. I broke mine a while back got a few when I ordered one and now.it cracked on my service guy. What adhesive to use to get the plastic threaded plug piece to stay in? See photos. Any thoughts?