Get a Ball Blue Book. It is the Bible on canning food.
I’ve never heard of putting lemon juice in tomatoes as you are canning. Just a bit of salt.
No, you don’t need to pressure can tomatoes, it ruins the texture, IMHO. The only thing I ever pressure can is green beans. Here’s a tip not found in the Ball Blue Book, it is perfectly safe to can your beans whole. All the recipes call for cut beans, but I prefer whole. I called Ball once about this and even the phone operator couldn’t answer my questions. But after 15 years of pressure canning whole green beans, I have never had a jar go South.
/johnny