I'll answer the piece I know the most about.
5.Do the tour in 10 days avoiding dirt paths ... take secondary roads ... wild camp if possible (I know there are limitations)
Thanks to anyone who would help us by posting answers. Cheers!
I think that 10 days is far too short to fully appreciate SJ to Santiago. That's what? about 90 km every day? Depending on the time of year you are planning on doing this that could turn out to be very draining (summer) or a lot of hardship - any other time of the year!
Secondly, it does not give a lot of time for the actual Camino experience or indeed the many, many sights to savour and enjoy. I cannot stress enough that the Camino is not like another bike tour. If you race through it you will miss out on so much.
Wild camping will be difficult and frankly exclude you from a large social aspect of the Camino experience. It may also have an impact on your Compestela if you do not have enough "stamps".
How are ye on the tandem on hills? there are a few, you know?
Also, a tandem will be more difficult to take on public transport in the event that you need to make up time.
There seems to be a lot of logistics (and costs) involved in getting your own bikes (and I would imagine more with a tandem) there to cycle for 10 days. A simpler alternative is to hire bikes there. There are companies with full support available. A Google will help.
To give more options for wild camping consider the Northern route (or variations thereof).
For more information from people who have done similar check out Journals on CrazyGuyOnABike.com.
If you are more interested in a tour than a pilgrimage then Northern Spain is a cyclist's dream and will ease up on the logistical constraints of your current plan.
Or consider Santiago as the start and end point. Lots of bike facilities (as well as cheap bikes!).
I cycled SJ to Santiago, then the west coast of Spain, then along the northern coast on the way home.
The Camino was fantastic (I took 16 days) and I wouldn't have missed it, but the rest of Spain was far more enjoyable for bike touring. I camped every night, except for the time on the Camino, proper, then I stayed in Albergues. I'd have missed out a lot if I didn't.