Send email only if a field has a certain value
I would use a technique similar to what is described in my answer to "How can I compare data comparison with values submitted in a webform?". For short:


Add an extra Rules Action to Add a variable, with a value assigned to it equal to your Webform data you want to use (and with an appropriate data type). You'd need 1 such variable for each Webform component for which you want to access its Webform data.
In your subsequent Rules Actions you can refer to the value of these variables you just added (that's the clue!).