That's how TTS works. The slower the pronunciation, the 'more careful' it is, and I believe here the change may be between pronouncing ę very clearly in the slow version and pronoucing it like e in the normal version.
You may also notice that in the slow pronunciation, the one-consonant prepositions are read as if the TTS was reading the alphabet.
There are rules for using comma before given words, when these words are connecting clauses. The case when "to" connect two clauses of which the second is the result of the first is described in the rule 90.D.1., let. b). Please note, that this is about clauses, and the usage of comma depends on words that it precedes in that function.
All about comma is in the chapter 90 of Polish Writing Rules.