I disagree that mommy dearest doesn't have any idea the beast she stirs up. She knows exactly what buttons to push w/her son to get him to project and jump on you. She is a controlling woman who now knows that you are strong enough to set boundaries and will not allow her to control your son.
If your son enjoys a tub bath, let him. My nephew enjoyed tub baths until he was 11 or 12 and now takes nothing but showers. He grew up and switched to showers on his own. As for jammies, some kids don't wear them and others do. It's a personal preference. These a minor decisions and again, your h needs to be more concerned about how your son is doing in school, not his bathing habits or jammies.
Again, he's on a roll and he's like a dog w/a bone, i.e., he's not going to let it go...but you can stop it by saying "h, I'm not discussing this any further. We will raise these issues in a co-parenting class or w/a counselor".
I still think his mother is behind this latest ranting. She's trying to rein you in so that she can dictate to you just how your son should behave. She's not a happy camper. If she could only see what she's done w/her own children and where they are today...that would give her pause for thought.
Please do not allow these projections to get you down. You are a great mother and you will do anything to protect your son.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.