Accidentally signed away my alimony. Can I get it back?

Almost certainly not, but ask the lawyer you used back then to be sure.

How big of a role will the past play in the fact my ex lost custody of her 2nd child due to the same pattern she's doing now?

The past doesn't always dictate the present. A lawyer needs details especially as to current events.

The answer likely is no but a lawyer would need to analyze the parenting plan to answer you.

You badly need a lawyer to examine all your finances to determine what property and alimony claims you may have. 17 years of commingle...

Can you sue if you are not married but engaged Alienation of Affection?

Plain and simple no. Sounds like you'll want to call off the engagement since you now know your fiance's true colors.

How can we legally terminate our parental rights?

You can no more unadopt a child than a birth mom could return her child years later to the hospital. Counselors and others may suggest parenting...

You also may want to swear out an arrest warrant. That and chargebacks will fix the bills. It's usually pointless to spend money suing criminals.

Can I still get my sons last name changed to his fathers?

Your priorities are wrong here. Get a child support case going. Then worry about other things.

What can I do if I was ordered to pay child support for a child (that I did not know existed) without a DNA test ?

I am betting it's too late but see a lawyer to be sure. A support case is lots more than just asking for a DNA test. Proper defense and motions...

When a parent is in contempt for a standing order,leaves state with child.Does this greatly help my case?

The order may or may not even be violated. If she was in the process of moving as you filed, a judge probably won't see it as a contempt, and you...