Nicolas Poynter has a BSc in chemistry from the University of Oklahoma USA and worked for 20 years as an analytical chemist in environmental laboratories and as a field chemist searching for underground petroleum leaks on crosscountry pipelines In 2009 he decided to focus on training and education because he found that he enjoyed this part of his job more than any other Nicolas now teaches physical science the first block of which is physics the second being chemistry at Choctaw High School in Choctaw Oklahoma USA

What is the correctly punctuated version of this sentence?
Nicolas Poynter has a BSc in chemistry from the University of Oklahoma, USA, and worked for 20 years as an analytical chemist in environmental laboratories and as a field chemist, searching for underground petroleum leaks on cross-country pipelines. In 2009, he decided to focus on training and education, because he found that he enjoyed this part of his job more than any other. Nicolas now teaches physical science (the first block of which is physics, the second being chemistry) at Choctaw High School in Choctaw, Oklahoma, USA.