Firstly I’m not here to suggest 50:50 is right or that I’m supporting your ex, we don’t know the intricacies of your life.
however, currently based on what you say he’s not being overly unreasonable.
having an affair is shit. But being a husband and a father are different, you may rightly not like him as a result but it’s still possible ( and usually positive ) for children to still spend loads of time with their dad. It’s possible to be a shit husband ( or wife) and a good dad /mum ( I know on here people often disagree this)
re getting the bus. On face value that’s not unreasonable. Many teens do this everyday. You mention additional needs and panic attacks. What support do they get ? What do they need? Does he agree /disagree ? Is it formal diagnosis? Is it documented ?
having some flexibility re travel is in itself not unreasonable.
what are the reasons they don’t want more time with him? Eg they can’t see friends, or fo sports or he had a temper or whatever ? Are they reasonable reasons ? Or is it they ( perhaps subconsciously) think they’d be betraying you ? If the former , it needs documenting and outlining.
Ultimately you can try to work with him to co
e up with a proposal you can all agree, or he can try to drag you through court ( if he pursues it - although I don’t think he’d get far)
what can you accommodate reasonably?