Alicia, I haven’t made it with fresh tomatoes. But I found this information on converting the amount of the canned tomatoes to fresh: A 28-oz can of tomatoes is equivalent to approximately 2 pounds of tomatoes, which is usually 10 to 12 tomatoes, so would need twice that since the original recipe calls for (2) 28 ounce cans or 56 ounces of canned tomatoes total. It would be 20-24 tomatoes and I would recommend using Roma or plum tomatoes so you’ll have less liquid than using Beefsteak tomatoes.
And then yes, you can add the additional herbs and onion to the mixture. I’m interested to see how it turns out, so please let me know!

Joyce,
that is a good question. I don’t see why it couldn’t be, but I didn’t freeze any. It was so good that I knew I’d eat it within the next couple days after I’d made it.