You're not being paranoid. It is your responsibility to protect your wife. What are her thoughts and feelings on the subject? Being mortified is a small thing compared to being the target of inappropriate attention.
You might try intercepting him... firmly. Step between him and your wife when he approaches. Switch seats at prayer so you're between them. Make it clear by your body language that you are not allowing his behaviour to go unnoticed. Make sure your wife is on board with you... she can turn away from him at the same time.
If your wife is not comfortable with the man's attention or with confronting him about it, feel free to do so yourself, privately, clearly, and directly. If he continues, take her with you. If he still continues, go to the elders. That's the biblical way to handle it.
If he tries to manipulate the situation or cause trouble for you, go straight to the elders or pastor, whoever has more authority in your congregation. Be clear, and address the behaviour that is unacceptable.
One more thing... because he is "powerful and senior", make a written record of every interaction. Email them to yourself so they are dated. That way it's not just "your word against his" should it go sideways. And, sadly, plan to look for another church.