Paul speaks of the peace that Christ gives as if it were a ruler. Possible meanings are 1) "Do everything so that you can have peaceful relationships with each other" or 2) "Allow God to give you peace in your heart" (See: [[rc://en/ta/man/translate/figs-metonymy]])
It was normal for Paul to speak of the heart as if it were the place where people feel most intensely certain conditions such as peacefulness. You should use the most natural expression in your language for feeling at peace. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Paul speaks of Christ's word as if it were a person capable of living inside other people. "Always trust Christ's promises" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Possible meanings are 1) because he has done great deeds or 2) because he has made it possible for people to speak to God and so give him thanks. (See: [[rc://en/ta/man/translate/figs-metaphor]])