I think you need to be very clear with your ex and firm with yourself so he can understand that he is fully responsible for the children on his days. Otherwise you cannot use his contact days to work more hours, catch up with stuff needing to be sorted at home or even rebuild your life, and by rebuilding your life I don’t mean finding a boyfriend, what I mean is rebuilding that very important network of support you will need around you as a single parent.
My ex wanted 50/50 but… he wanted me to take to school, pick up if he was traveling (he was a lot of the time) and most importantly, if DS was unwell or off school on his days, he expected me to take a day off work to care for him as his “job was more important than mine” or he had “run out of annual leave”, or he had “forgotten” and was away from the country, which obviously ended up in me losing my job after asking permissions to leave unexpectedly dozens of times. It also resulted in me having to work in more flexible roles with even less responsibility (and much lesser pay) to accommodate his career development, even when I was no longer getting any benefit of it.
When I decided to stop “helping” him I was branded a bad mother by the world and their dog, my friends and my family included, but some way he realised that his aspirations for contact were unrealistic if he wanted not to be distracted at work. (I didn’t do it out of pettiness but the clear reality that I couldn’t afford to lose my job as that was the one thing that was paying for the roof over our heads).
After a couple of years, I learned he did all this 50/50 “we are equal parents fight” because that meant he wouldn’t have to pay maintenance and it could easily affect my entitlement to UC: one night more than 50/50 at his house in a year and he would get the CB and UC, which would have rendered me unable to provide a space for my son to stay with me overnight. I would also have to pay him child maintenance even when he was earning 7 times what I did.