Great questions about NHTSA's response to Barr's findings. I've been to DC twice to push this issue, and have observed and learned a lot about NHTSA (although still not an expert—the Center for Auto Safety has the world's best expertise about NHTSA).
First off, NHTSA responses are normally measured in months or years, not days or weeks. Second, as a policy, NHTSA does not accept materials from outside the agency unless they have a "docket" open on a particular subject, to which the public can contribute materials. They were recently asked to open a docket on SUA and they refused.
I think they will re-do their Toyota investigation only by order of Congress, and so far, Congress has not reacted in any way, AFAIK. The best thing you can do is to contact your own representative and Senators and press them to propose or support a new investigation. The main committees in charge of NHTSA oversight are the Energy & Commerce Committee in the House and the Commerce Committee in the Senate.