Regarding detaching from your W, I'm not sure you have. On one hand you say you have no feelings for her but on the other you're really concerned about not talking to her, not doing things for her, etc. I think the goal should be to just be you. When you are home with the kids, being yourself, enjoying your family...and then W comes home....I challenge you to continue to BE YOU. Don't let her attitude, her comments, her coldness, or whatever impact the fun you are having. You control you.
I agree. Detaching is about your happiness not depending on what she does or does not do. It's HARD. I haven't been able to do it.
In regard to the S, there won't be negative legal consequences in some states. Consult with a L. However, if you still want to save your M (and I think you do) a separation will almost always be a bad idea. Once you're living apart, especially if there is no separation agreement or goals attached to it, the M is more likely to end. Think about this very carefully...
