Hi Montie,
I think you can discount an assembly error, ie not timing the gears, when you also have the bevel box damage. My feeling is this, either a tracta joint has failed big time, whilst driving the strain has been put through the bevel box, hence a lost tooth, also the planet gearing has been damaged by a locked wheel station being dragged along by the other wheels, stripping the teeth. The look of your bevel box, gives me thoughts that it might have failed through lack of oil, as that oil level also feeds the inner tracta, then it will be interesting to see what that looks like.
There are no gaskets on those hubs, in service, we used Hylomar or similar. I am not in favour of silicone sealants as it tends to set off before you are ready and can cause a sandwich, not allowing the two parts to tighten up properly. This then allows fretting and more problems.
I am looking forward to the next installment.....Tracta joints :-D