No it's not as simple as a 50/50 split, specially when your dad was cheating. Your mom may be entitled to alimony or a big lump payment from your dad, specially if he was making more money than her. If some of your siblings are under 18 and she has residential custody, she will also be getting child support for them.
But the good part is that none of this is your problem. It's theirs. After something like what your dad did to your mom you can't expect your mom to not be angry and handle things rationally.
It's pretty normal that she's mad. As to your dad, since he's the one at fault, his behaviour doesn't make much sense, but since I've been through my parents' divorce and have seen more than my fair share of couples going through similar issues, I can tell you the big secret truth the more men are at fault, the more they'll act like it's all the other person's fault. Your dad is a j*rk, sorry to say so, but it's the truth.
I think it's good you don't want to pick sides, but you may find that can be difficult and picking a side may eventually be easier than going on pretending everything is ok. I mean aren't you a little mad at your father for doing this to your mother? If you're not, well that's probably admirable but it baffles me.
I still haven't forgiven my dad and it's been 10 years now since he announced he wanted a divorce. To be fair, he's been awful throughout those 10 years, but still. If you feel better staying away, do.
But I feel maybe you have a responsibility to your younger siblings to be there for them, help them through and I would add set some things right (your brother turning against your mom on lies is a very dirty trick on your father's part. If it had been my brother, I would have spoken to him and told him the whole truth. I know it's not easy because I was the one that told my then 11 year old brother our parents were getting divorced and I'll never forget his reaction).
I am nearly 25 years old now, so just a bit above your own age and I've been in the situation for 10 years now and I can tell you that unfortunately, this is the situation you are going to have to live with for the rest of your life now. Things like not going to cousins' weddings because dad will be there or not knowing what to do when you get married (got married last year, didn't invite or even told my dad, same issue on my husband side, we had a hard time placing his father on the table so he'd be as far as possible from his mom and her relatives, in the end he didn't even bother to show up). Feeling awkward if you pass him on the street while you are with your mom (doesn't often happen to me since I live abroad from both of them anyway).
Not being able to tell him your brother is actually right next to you when he's looking for him because your bro doesn't want to talk to him, etc... I want to say you will get used to it and that's partially true, but there will always be issues when you have no idea what to do. My wedding was the big one recently. I felt bad about not inviting my dad even though I did not want him there at all and it took me a long time to decide I wasn't gonna be bullied into inviting him because of the "etiquette".
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.