This rubbish about staying together for the sake of the kids.
Children learn how to have successful relationships based on what they see at home.
Two people living together in eternal misery, or worse still trying to maintain extra martial affairs to fulfill needs, does a lifetime of damage.
My parents stayed together for us kids. You know how utterly soul destroying it is to feel like the cause of your parents unfulfilled relationships and unhappiness.
And if you think they don't know....your wrong. They always know.
I spent ages thinking there was some terrible secret our family were hiding.
The truth would have been much easier to bear.

All the best though OP, I do wish you all the luck, and hope things work out for the best.