The general tendency in this thread has been that the answer to the question “Who gets to decide?” is “The one who does it.”.
If someone cares a lot about pleasing their mother and mother-in-law by tidying up this way rather than that way, then they should go ahead and please their mother and mother-in-law. It’s not some great worthy cause; It’s a capricious desire to indulge the capricious desires of others. If you decide to do that, fair enough but do it yourself.
Disagreement between opinions doesn’t require all said opinions to be equally arbitrary. I haven’t said that I think it’s just about keeping away the cockroaches so kindly don’t fucking put words in my mouth. Perhaps it would help if the OP and Manda told us what elements of tidying up that matter very much to them. Perhaps they’re eminently reasonable, perhaps not.
OP, you’re staying with your partner for the sake of your child, correct? As someone who comes from a family that involved quite a few separations, I didn’t mind the separations anywhere near as much as I minded the behaviors of people who had become bitter, depressed and neurotic as a result of staying in a situation that was a bad fit. Have you considered that staying together may be worse for your child than separation? Does holding your current opinion about family separation feel like holding the opinion you used to have about porn, where it’s mainly based on anxious mental loops and How Things Are Supposed To Be?