I am going to bastardize a Sherlock Holmes thing here, but the gist is, instead of twisting facts to suit your theory, you have to build a theory that fits all the facts.
In other words, stop trying to find ways to make your husband not as bad a partner as all the evidence over the years has shown you that he is. I know the fantasy that he will he reform and turn into the man you want him to be is a powerful one, but it IS a fantasy, and this latest instance of lying and hiding things and then trying to make you the bad guy in it is just an another example in a long line of a examples -- a line that will only be as long as YOU decide to stick around for.
Focus on you and your son and you can't go wrong. Continue to do what you have always done, and you will continue to get what you have always gotten.
Sending you strength, patience and resolve.