Your initial 1-4 are all correct from what I'm seeing.
Second set:
1. Unclear. It is an animal of the phantom subtype, but it acts as the Phantom class feature, which certainly wouldn't require it.
2. Shared Consciousness is not a Spiritualist class feature, but a phantom feature. As such, the ghost mount retains this ability as it is not removed by the archetype.
3. As per the Phantom class feature on Spiritualist, it is a standard action to return it to your consciousness.
4. Unclear. This definitely needs clarification.
I agree with Serisan for the most part.
I had seen an argument that since the phantom can wear magic items, it should be able to keep them when using Phase Lurch unless the ability says otherwise, and if it can carry some physical objects while lurching, it may be able to carry a rider. Given the variety of opinions I had seen on the forums, I posted a request for a FAQ on the rules forum. Although there hasn't been an official response, I'd say that the general consensus is that even if a phantom can keep magic items while lurching, it would not be able to carry a rider. It would definitely lose all carried items when not manifested (as per the standard phantom rules). I probably should have also asked whether the phantom manifests with a saddle and bridle as well, or if the rider must use the rules for riding bareback.
If you're using mounted combat, you'd use Ride instead of Handle Animal for most functions. While dismounted, it should operate as a phantom for control issues, although the low intelligence would make complex commands difficult. I have not seen anything to suggest that it would get tricks as a standard animal companion would, so the Attack trick is a moot point.
A further thought - since the ghost mount has a specific attack sequence that does not reference the standard phantom attack rules, I would say that the damage would not scale up as per the standard phantom; however, the magic attack is a "special" ability so it would not be affected by the change to the attack.
And let's not forget that even if you choose a Wolf, it will have hooves. Presumably it can wear magical horseshoes. ;)
3 from the first set is true, but there's an equivalent feat for phantoms now. The class feature name is different, but counts as the correct one. That should help with multiclassing.