I had purchased my condo on my own credit several weeks before our marriage. After 4.5 years, my spouse walked out. Now, 4.5 years after that and after 3+ years of me trying to save the marriage and giving them all kinds of money ($40k+) over that time, they want me to sell the home that I have been making ALL the payments on for the past 9 years. We did do a refinance, and a second mortgage, so they are still on the loans. My spouse also filed false tax returns and lied to me about income and living situation for years. Yes, I am stupid. But is this person still entitled to half my home?
You are not stupid - you have been taken advantage of, unfortunately.
You need to seek the advice of a local experienced divorce attorney. The answers to your questions are complicated and depend on the overall facts of your case. Divorce is complicated and requires expert assistance. As you are probably aware, Wisconsin is a marital property state. Even though you bought the house before the marriage, under some circumstances the Court may decide the property is marital. The filing of false tax returns is also a big problem about which you need expert help to protect yourself against any possible claims.
Answering this question does not create an attorney client relationship. It is not legal advice.