Hehe happy birthday man. Here's a picture of me standing next to a 13-14 footer last harvest. It was a Pineapple/G13 cross that the clone guy called "Scary". Notice its about 12-13 feet wide as well

This picture was probably taken sometime in October. Believe it or not, we only pulled about 3 pounds from this gigantic bitch, but the smoke was outrageous

As far as container size, I think a 15 or 20 gallon bag/pot would be sufficient to avoid being root bound before the last frost. I always use 5-7 gallon containers just because they are easy to work with, cheap, don't take too much soil to fill (im a broke ass lol), and as long as you don't start TOO early, they are big enough to support a large plant with lots of roots. I usually start indoors around Feb-March and plant in the ground Late April-Early June. Again, good luck and hope your shit goes well my man.