How to modify information in "meta http-equiv content" section in (response?) header?

1) Am I correct that it is the HTTP_RESPONSE that includes the information depicted by pscout.txt?

Yes.

2) The "backendnode1" information is not in the Body of the response. It is my understanding that this means that a STREAM profile will not help. Correct?

The "backendnode1" information ISin the Body of the response.

"the HTTP_RESPONSE" is "the Body of the response"

Add -i to your curl, to include the response headers, in addition to the response "body".

And yes, a stream profile would be able to modify that html content. https://devcentral.f5.com/wiki/iRules.STREAM__expression.ashx