What is the dalvik speed patch? Lately I've been hearing about a dalvik speed patch to supposedly increase the interpreting speed of apps through the dalvik JVM. The only mention on Google is Facebook's "hack" of the dalvik JVM to allow the Facebook app to install on legacy phones. I am sure this is not a dalvik speed patch. 

Post where the patch is briefly talked about:

"New score...PA 3.99 RC2 + Franco r184 + dalvik speed patch.."
https://plus.google.com/105415059081329756565/posts/4i8GDm47bnv

So what exactly is this dalvik speed patch?
There's absolutely no magic here caused by a mysterious "Dalvik Speed Patch". The Author said that in the comments himself by stating:

Lol... I just mention dalvik speed patch, actually it's a kanged lib file...


So it's just a wording issue that you took as a rumour.

The higher Antutu benchmark scores are very propably caused by overcklocking using the Franco Kernel only.

Regarding your second thought about the FB hack:
The FB hack has has nothing to do with this question. By the way, it's super ugly and something Facebook should be ashamed of: http://jaxenter.com/facebook-s-completely-insane-dalvik-hack-46376.html