833 Tail housing leaking through bolt hole for Rear Mount?

I think I have traced my 833 tail housing leak to on of the bolt holes for Rear Mount? Is this hole visible to the transmission fluid, or is it blind? Do I need to seal it with teflon or rtv? I also noticed the bolt is not seated completely, and I tried to tighten it but it does not move, sloppy work by the previous owner...
Not sure if it is bottomed out, or too long of a bolt, or cross-threaded (doubtful)?

clip-06 Nov. 08 13.36.jpg