1. Yes, PVC is fine for surface exposure, even in garages. Local codes may require schedule 80 PVC, which is thicker, in exposed areas like a garage. Where i am schedule 40 is acceptable. But if it is to be inspected it's a good idea to check with the local Electrical Inspector for any additional requirments he may have.
2. Yes, the disconnect in that link will work just fine. Again, it cannot be closer than 6' from the inside of the tub wall. In some areas around here it is required for the feed breaker to be GFCI also, as to protect the wires, as short as they may be, that are outide feeding the disconnect. The disconnect is more for the servicing technician to be able to isolate the spa for servicing purposes. I love the tutorials in the link you provided, the women are quite endowed.
Good luck and let me know if you have any additional questions. And by the way, the 4x4 and HVAC on the TB are still working fine. Don't wanna jinx it, but usually the problem would have returned by now. I think we actuallly fixed it roadie!
Muchas gracias again!