WE are both correct....the question is does OP really know what's on wife's account with her son.
Hogwash.
As per OP: wife "transferred a joint account into her own name without my consent and put her son down as beneficiary."
That pretty clearly means the account is in her name. The son as beneficiary only has an interest in the account if she dies.
Look, I'm not out to get OP, and the wife is no likely angel (we are, after all, only hearing one side), but if OP has competent legal council and your misstatements are giving him second thoughts, you are doing him a disservice.