I made another 9 gallons of sauce this weekend. This time I used all Romas. I cut the tomatoes in half horizontally and placed them on sheet pans, cut side down and roasted at 500f for 25 minutes until the skins became almost blackened. Much of the water had drained out into the pan- I got a gallon of this juice and canned it for future cooking. I put the roasted tomatoes along with roasted garlic through my food mill and cooked down the sauce. The result was a thick, intensely flavored sauce. I finally got the results that have been eluding me for over a decade!
Thanks again to everyone for the comments! I didn't necessarily use anyone's exact technique, but you all helped shape my thought process and guide me to tomato nirvana!