[sutyak]

That's a really strange part to fail. Typically there is zero pressure on it. It's lightly pressed into place and then a snap ring behind it. It would have had to come in contact with the case or sensor to break, unless it was already cracked when installed.
So that leads me to believe that cluster shaft is bent as you thought, and/or the bearings are toast.
I'd lean towards buying a second transmission, installing it, and then tearing into this one to see what happened and so you'll have spare parts.
I've rebuilt a couple of these, so if you did want to tear into it I could help depending on my schedule.