My thought is that you should speak to a lawyer who is experienced in these kind of disputes. Bringing in a lawyer to represent you pretty much burns the bridge

My thought is that you should speak to a lawyer who is experienced in these kind of disputes. Bringing in a lawyer to represent you pretty much burns the bridge but it sounds like you will either want or have to leave anyway. If this is a large company, they do not want to get involved in a protracted dispute, especially if it might become public. This is true regardless of what you have done that might legitimately make them want to get rid of you. Yes, you don't want to ruin your own reputation as an employee for a future employer, but they have much more to lose in most cases. You would be surprised how far companies will go to avoid outright terminating someone. In past jobs I have been in management and had to deal with people who had anger management problems, drug problems, and sexually harassed co-workers. Despite the documentation for these issues they were given up to 6 months to find other jobs and/or terminated with several months of severance for signing an agreement they wouldn't sue. A lawyer will generally give you a free consultation and could write a letter on your behalf for a few hundred dollars. If your case seems to have more merit, they may be willing to take it on contingency.