Man, sigh of relief.
phew
Root cause of issue: Drain bolt was probably a cheap replacement
That appears to be an OEM drain bolt, to me at least. That magnet on your plug (that you courageously removed



) appears to be consistent in appearance with OEM Honda and Acura ATF drain plugs I've removed from 4 and 5 speed Odyssey, Accord, and Acura TL automatic transmissions.
I do believe
pkrface called it.
That side pic of the two drain plugs looks familiar to me. I've seen this before. Once. Years ago, on my used 1998 Accord, I think they just kept torquing it every time it started to leak, and kept driving. The previous original owner appeared to had never changed the ATF in over 150,000 miles, and that crush washer was curled up a bit ... but
it looked nothing like yours. Yours appears to be curled completely over the rim of the drain plug.
Also like you, I thought I was going to break my 3/8" drive ratchet in my attempts to loosen it, so l also switched tools. I chose to use a Klein Tools 3/8" drive breaker bar. High dollar tool, but very exact fit, and strong enough to do the job. I was almost to the point of driving over to a mechanic and have them do it for me, but I got lucky and it came loose.
metal appeared softer than stainless steel
Pic is from an Gen 6 Accord. OEM drain plug. They can eventually rust; the OEM drain plugs don't appear to be made out of stainless steel. Also, un-coated stainless fasteners and aluminum threads are not compatible. An electroplated regular steel fastener is what most OEM's use.
The shiny coating is an electroplated CPC (corrosion protective coating) similar to what you might see on various other fasteners on Hondas and Acuras (it almost has a silvery-goldish sheen to it). It helps a steel plug like that to be properly tightened and removed many times over the life of the vehicle without degrading the aluminum threads in an aluminum casting like your transmission case.
Having been almost in the same boat once before, I definitely agree that your first ratchet was not a good fit...especially due to the damage to the plug (and you have strong arms). I would also agree with the other posters on this thread that the previous guy grotesquely over-torqued it.
I'm amazed with your rig that you used to keep it from backing out on your second attempt.
Man, this whole thread was so nerve-wracking, I'm going to go ahead an make myself a White Russian this morning.


Again, heartiest congratulations. I know a little of your anguish, but only a little!
OF