My first questions is why you need aux air brakes? Im assuming you have a air brake trailer. What kind of load, are going to pull with a two ton truck that has air brakes ?
I personally had rather use electric brakes on a trailer that you would pull with a two ton, but if you have a trailer with air brakes then lets see if I can help.
Not knowing how many air tanks you have, I would say try it the way it is and see if you have enough air capacity, you will know when you hit the brakes a few times
You will have to install another cab brake valve for the aux (trailer) brakes. Yes you can tee in a line, to the regular brake line, but dont get caught by the DMV. Its a PITB to install a aux air system on your truck, but it can be done.
Go to a salvage yard and find a truck like yours and see how its hooked up.