The long roasting mellows out the garlic, I think... but then, I like garlic. If you're not so fond of it, reduce it, or leave it out and toss in an onion instead.
I'm not really sure about the quantity from the small recipe, because I usually make it in a huge turkey roaster pan, heaping the pan up and sometimes tossing in another few quarts as it's cooking down... that yields about a gallon of sauce. The yield will also vary according to how juicy your tomatoes are (more juice means less sauce once it's cooked down... I like to grow really meaty tomatoes with small seed cavities, so I don't get quite as much juice from mine) and according to how far you cook it down. I've learned to leave a little juicy stuff in the pan so it goes through the food mill better. :-)
Try it... if it's too strong or too garlicky, you can always add more fresh tomato to the sauce before freezing it. My folks like it about diluted by about half with plain tomato sauce. I think you'll love the flavor!