Editing is coming along -- this should be out no later than tomorrow - hopefully sooner.
In the meantime, this part of section 19 (book one) is clearly one of the sections that is most critical - here is the Rackham version, with the focus on "that in the sum of things everything has it's exact match and counterpart."
Here is Rackham's Latin:
It looks to me like that is a rendering of a section of "ut omnia omnibus paribus paria respondeat," so Rackham's "match and counterpart" is as open to question as is Yonge's "everything in it is made to correspond completely to some other answering part." In this instance Yonge's "answering" may be a better rendering of "respondeant" than Rackham's "exact match or counterpart." The decision we make on what words to use is going to greatly influence one's conclusion on what is being said. What would seem most likely for an Epicurean to be thinking in terms of "answering" or "corresponding?" We know the basics of Epicurean physics and canonics which cannot be violated in answering the question, so what are the possibilities?
This is a line at which we'll want to train our best big guns of Latin translation expertise!