What is the ruling on a husband continuing to anally penetrate his wife after she has become accustomed to it and prefers it, knowing its prohibition, and is he permitted to divorce her despite her righteousness and the effect of that on the children?

Anal intercourse is forbidden and a major sin. You and your wife must immediately and sincerely repent to Allah by abandoning the sin, regretting it, and resolving never to return to it. It is not permissible to accuse your wife of indecency without proof, and her engaging in this abomination does not prove her indecency. Keep your wife and treat her with kindness, and think well of her. If you cannot stop this abomination with her, then divorce her and marry someone who rejects this act.