Sorry for may late reply, but I hadn't got much time in the morning.
Let's try to analyse your translation from Latin:
Although he became accustomed to control the feeling of getting angry,
1. I am not English expert, but we should say:
"be accustomed to (doing) sth" (not "to do" sth)
2. "moderate" isn't a verb. It is an adverb --> not excessively, moderately... so we should say: "he got moderately angry" or "he irritated a little".
he would still prefered not to had much influence upon it:
1. to had --> ???
2. he would still prefered --> what kind of tense did you use? Maybe you meant "he would prefer", it will be FUTURE IN THE PAST, but we can't use the tense. It doesn't fit here. We rather should use PAST SIMPLE: "He didn't want to be able (to get angry)" or "he prefered not being able..."
3. "(to have) influence upon it" doesn't fit here too.
He tought it the most agreeable/acceptable not to knew who had sinned and what kind of sin.
1. most agreeable/acceptable. I wouldn't choose these meanings here.
"gratissimum" we can translate here as "the nicest" "the most desired". I translated "the greatest", because it is more general word and expresses the real meaning here.
2. not to knew --> ??? (it is not correct English, sorry. The same kind of error which is above: "to had"
Well. I'm really glad you want to learn Latin. We need more Latin translators here... Remember you can always count on my help.
My best regards, Jurek!