Dad is cheating and it’s a history

So my dad married mom when she was just a child. His first mistake to leave 2 children and a wife to marry a child?! And growing up my siblings told me how he abused her and she did nothing even knowing that he can be in jail for everything. He brought mistress in home and introduced to me when I was young. I took the mistress to mom and mom found out. They had a huge fight and dad beat up my mom. After so many years my dad started doing stuff for family and me so I thought he changed. I accidentally saw his message in family iPad and the texts were weird. A woman was asking to meet him desperately And he replied “not now.” Again another text popped up from a uncle, his friend. He sent photo of a woman and said she has some good virgin ladies and dad agreed to check it out tonight. I am scared. Should I tell my mom? Mom is so sick and just got out of operation a few weeks ago. I cannot ruin her health but she deserves to know what he’s doing. I am scared and embarrassed to confront dad. I am here knowing he’s somewhere out there cheating on mom and it’s wreaking my mind. I can do nothing to save this family. If I go to uni after letting her know, will she be able to handle things with dad? I am 100% sure she will cry and shout but will never be ready to leave dad. What should I do?!