You can change what NVDA says for any punctuation or symbol in the Punctuation and Symbols settings, NVDA+N,P,P.  I presume you mean the period at the end of a sentence, in which case the very first item you will see in the list is for the period, sentence ending, with its replacement as "dot."  If you get yourself to the Replacement box, erase dot, type period (spelled out), and hit the OK button that will be changed.

I'll leave the other two to others.
--

Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363  

Science has become just another voice in the room; it has lost its platform.  Now, you simply declare your own truth.

      ~ Dr. Paul A. Offit, in New York Times article, How Anti-Vaccine Sentiment Took Hold in the United States, September 23, 2019