When we talk about adultery, we often talk about sex. But for God and the Israelites, adultery was about commitment to the covenant. Out of 26 verses in the Old Testament where the word for adultery is used, only 9 are about actual marital infidelity. The other 17 are about Israel's faithlessness to the covenant with their God.
Read Ezekiel chapter 16 to get a glimpse of the seriousness with which God viewed the breaking of the covenant.
God is a covenant keeping God. God limits God by the making and keeping of covenants. We cheat because we want to do what we want. But when we are faithful, when we honor our commitments, to God and eachother, we are behaving like God.
Discuss the questions at the beginning of this post.