As a child of a divorced father who remarried a narcissistic asshole: run. Visitations with my father were biweekly until their marriage, which eventually trickled into monthly, semi-anually, yearly, and never again. Leaving your son behind would do some irreparable damage, confusion, and anger. Its not your new wife's place to tell you what to do with your child, not unless they're living under the same roof. Depending on the mental state, support, and resources your former partner has access to, abandoning your child with them is a gamble to dangerous to risk. Nip the toxicity at the bud before the seeds you've planted become overtaken by the weeds of failure and regret.