Is the wife entitled to seek and obtain a divorce due to her husband forcing her to engage in anal intercourse, his unreasonable suspicion of her, and his accusing her of having a relationship with a young man since the beginning of their marriage?

Anal intercourse is forbidden and a grave major sin. It is not permissible to obey one's husband in this matter, as there is no obedience to a created being in disobedience to the Creator.

If your husband forces you into it, there is no sin upon you as long as you are coerced. However, you must advise him and explain the Shari'ah ruling to him, and not enable him to do so. If he does not respond, you may take the matter to a judge and seek a divorce, and there is no sin in mentioning his misdeeds to the judge or to a mediator.