Neither I nor my parents have been through a separation or a divorce. I have no reference to use to offer any significant advice.
I have witness two divorces that went relatively smoothly. The one thing they had in common was they didn't use the children to try to leverage their position when untangling their two lives. One couple didn't have children, so it was a non-issue. The other couple just agreed to keep the children out of it and follow the courts direction and stuck to the agreement.
I don't envy your situation, nor Martha's for that matter. I sincerly hope you both can work through the process with respect for each other.