My apologies for the delay in responding to your e-mail. I am so sorry you are going through this, and I especially am sorry for the confusion and incompetence displayed by officials of the Church. Your patience is admirable.
The difficulty is that the Church presumes in a situation like this that the husband's first marriage is valid until it is declared null or until his first wife dies. That means that technically, for a couple living as husband and wife, that they are presumably committing adultery (from an objective perspective). Since this is a grave sin, it's incompatible with the repentance required for conversion and Baptism is not possible.
It is precisely because the church marries and recognizes the marriages of Catholics and non-Catholics that this is an issue. If the church didn't recognize your husband's first marriage, he'd be free to marry you, but because it does (until proven otherwise), he isn't.
If your husband's ex-wife is not married, there is not an issue with her being baptized because there is no violation of the marriage going on. However, she will be unable to marry without getting a declaration of nullity ("annulment").
The alternative to your husband getting another declaration of nullity for his first marriage is:
- to give up your marital rights and live as brother and sister until his ex-wife passes away, or
- she gets a declaration of nullity for her marriage with him (which is basically the same as he getting a declaration of nullity from her).
This eliminates the formal act of adultery in the equation and enables conversion. I'm not sure you can convince your priest that you will adhere to this, but it's the only other option I see.
You may wish to retain a canon lawyer for this if you don't already have one. There may be more obscure options, but they are very unlikely to be granted. Maybe you can find a technicality or something.
The reason your son could be baptized is that that does not involve violating the marriage that your husband still, in the eyes of the Church, presumably has with his first wife.
It's a tremendously difficult situation and I really feel for you. The choices are unenviable. But Jesus rewards us when we make sacrifices and hard choices for the faith.
29 And every one who has left houses or brothers or sisters or father or mother or children or lands, for my name's sake, will receive a hundredfold, and inherit eternal life.
Matthew 19:29 (RSV2CE)
I suspect this is why your priest won't give you a direct answer, because the situation is so difficult.
I will pray for you and your situation.