A: Being legal and having consequences are two different things. Just because you may be able to leave does not mean you will not have consequences for doing so. First of all, the two of you are still married which means you would need to get a divorce. Second of all, you will be obligated to pay child support and possible other expenses to help support your children. Third, you are leaving behind YOUR CHILDREN who are innocent bystanders in the poor decisions made by your wife. They should not be adversely affected (and they will be if you up and walk away) because of you or your spouse's decision making.
A: Good practice is to redact SSN from the tax returns. As far as having a case, unlikely. In order to have a case you have to be able to show you were damaged. I am guessing that other than having your SSN passed along without your consent you have not suffered financial harm as a result.