I think you will find the site linked below, written by a friend of mine who is an elder at a PCA congregation in VA useful:
Biblical Self-Defense: What do the Scriptures say about using lethal force for self-protection?
I don't have time for a detailed reply tonight, but I'll mention that the WLC touches on this in questions 135 & 136.
Question 135: What are the duties required in the sixth commandment?
Answer: The
duties required in the sixth commandment are, all careful studies, and lawful endeavors, to
preserve the life of ourselves and others by resisting all thoughts and purposes, subduing all passions, and avoiding all occasions, temptations, and practices, which tend to the unjust taking away the life of any; by
just defense thereof against violence, patient bearing of the hand of God, quietness of mind, cheerfulness of spirit; a sober use of meat, drink, physic, sleep, labor, and recreations; by charitable thoughts, love, compassion, meekness, gentleness, kindness; peaceable, mild and courteous speeches and behavior; forbearance, readiness to be reconciled, patient bearing and forgiving of injuries, and requiting good for evil; comforting and succoring the distressed,
and protecting and defending the innocent.
Question 136: What are the sins forbidden in the sixth commandment?
Answer: The
sins forbidden in the sixth commandment
are, all taking away the life of ourselves, or of others, except in case of public justice, lawful war, or
necessary defense; the neglecting or withdrawing the lawful and necessary means of preservation of life; sinful anger, hatred, envy, desire of revenge;all excessive passions, distracting cares; immoderate use of meat, drink, labor, and recreations; provoking words, oppression, quarreling, striking, wounding, and: Whatsoever else tends to the destruction of the life of any.