I have seen on some older Onkyo's that the laser will focus but if the
inside (limit) switch has not been actuated, will just sit there and spin.

That switch is also ok and working well.

Also, if somehow the disc rotation is backwards (...)

No, the direction is correct.

Speaking of the decoder IC, it could be suspect at
this point, especially if it's a CXD2500 type

Unfortunately it's one of those .
I think that this will be the player's epitaph. I'm not willing to try
and replace such an IC, provided it's still available.
Mark, thank you very much for your help and suggestions!

Cheers, Lasse