First, with your child going on the field trip, your h gave you his reasons (which are valid) as to why he feels she should go. You disagree, which is also perfectly acceptable. My thoughts are, though his reasons do have some validity, he is still just trying to be controlling (and using the kids as pawns). I look at you as the primary parent so what you want goes.
As far as your communication with your h...Here is where I wish I could give some of you going through divorces a glimpse of the future. Worrying about how you communicate during your divorce will not generally effect how you communicate AFTER the divorce is over. Right now, feelings and emotions are driving a lot of what is said, how something is perceived, or attitudes toward the spouse. After the divorce is over, and feelings go away/calm down, the communication does get easier (and better). My advice to you is to not worry about trying to say something the perfect way. It is stressing you out too much. Just tell him what you want and/or your decision on the matter and move on. If he emails you nasty emails, delete them (or save them for your lawyer). If he tries to call you about it, don't answer or just hang up if he gets riled up. I have a friend who is going through this right now and she is just so stressed out because she worries about him emailing her or texting her mean things. She feels she should just go along with what he wants so it doesn't happen. You have the power until you give it up.
My response to his email about the field trip would be this...
"I've read and thought about your views about sending D9 on the field trip. Though I disagree, I appreciate you explaining it to me. I am going to let her skip this field trip."
Don't stress out about his reply because you already know it's going to come. Just ignore it or save it for the lawyer.
As far as custody goes, of course that is a big deal. That is something you fight like mad. The only reason he wants it (or is saying he wants it) is because it is another way to try to control you. Do you really think that is what he wants? No! He is just using your kids as pawns again.
