Thank you for your kind words!
You don't want to bascule excessively, but neither do you want to hollow the back (particularly with a diagonally gaited horse). With a diagonally gaited horse a touch of bascule would not necessarily be bad. But you want to avoid that Mythbusters tradition that goes "anything worth doing is worth overdoing"!!!
If the horse horse is going well and you have good communication with the snaffle then stick with it. But if you need more "communication" on the trail or in open country or in a more stressful environment (parade, demonstration, etc.) then use the bit that gives you that "little something extra." I was once a "snaffle bit Nazi" but my experiences in military horsemanship convinced me that I was wrong in that assumption. My personal goal is to train myself to use a full double bridle with bit and bradoon and then start using that with our Marchadors. I'm about half way, using four reins on Pelham bit. In many ways that an excellent approach as it gives the rider the option of using snaffle or curb action as required by circumstances.
I'd add a couple of books to your list. First are the three, small volumes from Dr. Deb Bennet on Principles of Conformation. Last time I checked they were about $13/ea. At Amazon. She walks through the principles of equine conformation in a very readable and understandable manner. It's not always spot on for the gaited horse. Still, at the end of the day there are but a very few conformation deviations that benefit the soft intermediate gait. The adjective "gaited" modifies the noun "horse." We should always keep that in mind.
Second, I'd add Horsemanship and Horsemastership, Vol. I (Education of the Horse and Education of the Rider). This was the basic text at the Cavalry School at Ft. Riley, KS from the mid-30s to the end of the Horse Cavalry. It is an outstanding guide because it addresses training horse and rider in a very consistent manner. For example, if you want to learn a correct turn on the haunches you can read in Part 1 what the rider must be doing and in Part 2 what the horse must be doing in consitent language. That, frankly, is a failure in many modern texts on training and instruction. For maximum benefit get the three DVDs of training films used to instruct recruits. The whole package is under $100. Find them at U.S. Cavalry Association Store .
Now you've got some stuff you can ask others to put in your Christmas stocking!!!
Good luck with your horse.