OP, I didn’t want to read and run. I’m very new to Mumsnet and in fact, it was my experience with my abusive ex that led me to seek advice and support here too.
I’d never heard of the term ‘gaslighting’ until I read it on here and I think this is what your ex husband is doing - he’s minimising his behaviour whilst making you doubt yourself and questioning whether you’re doing the right thing.
You come across as a loving, caring wonderful mum who only wants the best for her DD. You’ve never stopped contact between your DD and her father, you’ve always made her available and have been more than fair in accommodating him and his work. To be honest, I think he’d behave this way if he worked in any job - not just the military.
You’ve done everything the correct way - you’ve logged everything down, seeked legal advice and informed the Welfare Officer and he continues to behave this way. Demanding you to take the letter is harassment. It should have been handed to his solicitor - you know this OP. HE is in the wrong.
I didn’t have anyone else for handover either but my Ex did - does your ex husband have anyone who can do pick up/drop off? Can you arrange to meet in a public place rather than your home - I think you’re especially vulnerable at home. So you can walk your DD to the pick up place, give her a kiss, hand her bag over and walk away. You don’t need to engage in any conversation.
Come on OP - be strong. For what it’s worth, I’ve had six years of bullying, missing contact, not turning up to school events, not paying maintenance. The final straw came this weekend in fact, demanding me to to travel four hours to drop my DD off at his housewhen the Court Order said half way only. I said ‘no’ and he replied with “then there will be no more contact”. In my case, the controlling of me became more important than our daughter - and yes, he is the one who took me to court too!