My mother believes in Buddhism.
I don't really like her because she sanctimoniously criticizes people.
His family is very religious and spiritual, so they don't drink any alcoholic drink other than spirits.
What you believe in your heart, and not in your head, is your faith. This is something that doesn't follow logic, it's all heart belief, it's all faith.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. Just note that しん changes to じん.