Is the proportion of vinegar to olive oil be right?

If the ratio sounds wrong to you (it does to me!), start with the ratio that sounds right - it's all a matter of taste - and adjust to make it exactly the way you like it once tossed with the ingredients. Let us know, please, what you end up with here. I'm curious! Thanks. ;o)

Also keep in mind the walnuts, which contribute fat and - if considered part of the dressing - more than restore the traditional balance of fat and acid in a vinaigrette.
I would taste the whole salad, including nuts and tomatoes, then decide on any adjustments to the oil or vinegar.

It would be for me— I like very tart salad dressing— but may not be for you. (It’s also too garlicky for me.) You could always make the dressing, then whisk in more oil to your taste if it’s too tart.