How can I expose the father of my child [51M] as a serial cheater?

Fifteen years ago, I had a brief relationship with a man I’ll call Martin while living in Texas. This led to the birth of my beautiful daughter, whom I’ll name Amelie. When I informed Martin of my pregnancy, he revealed that he had a girlfriend named Nicola who was six months pregnant herself and had experienced multiple miscarriages before. I was taken aback and distressed, but I had already fallen in love with Amelie through her ultrasound images. Nevertheless, I chose to continue with my pregnancy, knowing I would be a single mother, as Martin assured me he would help raise our child. However, he went back on that promise and abruptly left Texas for Arizona when I was four and a half months pregnant. He moved there with his girlfriend and soon welcomed their son, Ben, who is four months older than Amelie. After I gave birth to Amelie, Martin visited her when she was three months old. When Amelie turned two and a half, he relocated back to Texas and started maintaining regular contact. He even brought Ben along for playdates at my house. During our conversations, I learned that he had another child, Claude, with someone else in Arizona, who is younger than both Ben and Amelie. While I found his choices irresponsible, my priority was Amelie. Martin struggled to find steady work in Texas, so he moved to Wyoming, followed by Claude’s mother to keep their relationship intact. He also suggested I move to Wyoming, which I found absurd, considering my life, family, friends, and career are all based in Texas. Unfortunately, he wasn't able to secure a job in Wyoming, and I noted that he had many low-paying, temporary positions over the years. Amelie grew up without a strong relationship with her father, although he remembered her birthdays and holidays. As a single mom, I didn’t want to travel to Wyoming for visits, preferring to take Amelie to cities like New York or Mexico instead. However, since Amelie expressed a strong desire to see her dad and he couldn’t afford to visit us, I took her to see him. During our visit, Martin made an effort with Amelie, taking her out to eat and buying her gifts. Meanwhile, he had two more children with Nicola and revealed that he had a third child with someone else, totaling six kids from three different women. Amelie, who is autistic and has a keen sense of justice, feels uneasy about her family’s dynamics. I genuinely believe that Martin is a serial cheater. While Amelie wants to connect with her siblings, Nicola is unaware of Amelie’s existence. This situation brings us to the present: Amelie wants everything to be revealed, but I’m uncertain how to approach it. If Nicola learns of Amelie, it could provoke anger from Martin or lead him to further distance himself from her. In June, Nicola will come to Texas with Martin to visit her family, and I’ve considered discussing Amelie with her when she has support nearby. I worry, however, as Martin has exhibited violent tendencies; after Amelie was born, he mentioned having been violent with Nicola, which shocked me since he didn’t seem that way when I first met him. I attempted to reach out to Nicola’s sister for support, but she hasn’t responded, and I haven’t met her in person—only contacted her via social media. Each time Martin has fathered a child, he has forced Nicola to relocate, which adds complexity to the situation. Moving forward, I seek advice on the best approach to reveal Amelie’s existence while ensuring her safety and that of Nicola. I recognize that societal views on half-siblings and step-siblings can often be traditional, but I want Amelie to foster a positive relationship with her half-siblings. I hope Nicola shares that sentiment and would want all the children to know and love each other. Is that too much to hope for? In summary, my daughter’s father is untrustworthy with six kids and four different women, including a long-term girlfriend. Amelie desires recognition and relationship with her siblings, and I’m seeking guidance on how to disclose this safely.