I’m not Jewish so can’t speak to that specifically but have experience with being in these kinds of settings and the target of comments for other things.

It seems like you are definitely going and want to support your wife. Maybe the guy will be too busy focusing on getting engaged to have time for antisemitism but he sounds like a dick so that’s unlikely. My go-to is to 1) ignore indirect jabs (aka if he says things that are clearly implying something about Jews without specifically naming - he’s trying to upset you so don’t engage) and 2) to politely disagree with direct jabs and then pivot the conversation.

If he says it directly to you or in a group or 3-4 people: “I wouldn’t agree with that characterisation”, “I don’t believe that is true”, “I’m uncomfortable with the way you are framing that” and then move on - turn to Janet and say “how is xyz” or John and say “did I hear you are a keen golfer?” and keep it moving. You don’t have to argue but you can assert boundaries. It he tries to insist or argue just go with “I’m here to celebrate the engagement, let’s focus on that - do you have any thoughts about the wedding?”

In larger groups I’d just walk away from the conversation or excuse yourself briefly from the table or go for a glass of water etc. You don’t have to stick around and listen.

Make an agreement with your wife in advance that when you’ve reached your limit of comments that you’ll both leave, even if it’s early. You are supporting her but it’s okay to want and expect her to support you too. Knowing you have an out when you need it can make it more bearable.