I have just uploaded beta 2 of WordPress Google Form v0.54. This update fixes the problem with the validation meta box not allowing adding additional fields (a jQuery script was not loading correctly) and also fixes the issue with range checks I mentioned in the beta 1 announcement. At this point I believe everything is working correctly.
I have put together a Validation Demo Form that you can play with to see how it works. There are some images below from the demo form running in my development area including how I set up the validation information when creating the form.Google Forms Beta (231 downloads)