There are some mistakes in the text, like poteva, should be potevano.
You probably already met "from how" in english. "From how he was studying, it couldn't have been different."
"Suoi" means his parents, read it as "i suoi (genitori)". We say stuff like, "I suoi sono separati". They are the subject of 'sono'
In this case, read "Pensa (tu)" as "you know," in english, or "imagine this,". So the subject is one of the two unnamed people talking.