Co-parenting advice

I don't really know where to post this - but I'm just after some advice really I guess. Me and my ex partner split up a year ago, the ex only moved out in May this year so now we co-parent to a nearly 3 year old - he is there Monday Tuesday Wednesday day and with me Wednesday eve, Thursday and Friday and then we alternate weekends between us. Apparently he is a nightmare when he is with the ex, here he isn't.. it's like he is two completely different children.. The ex thinks it's because we need to be more consistent with bedtimes, 7.30/8pm every day to fit in with when he gets home from nursery. I've tried to explain that's not always a possible bedtime especially when he doesn't nap, which is very regularly lately - think he is getting ready to drop the nap - so he goes to bed around 6.30pm because he just can't stay awake any later without the nap. I've said it would be cruel to force him to stay awake until 8pm when he is literally asking for bed saying he is "too tired".. I honestly don't think an varying bed time is the reason for how his behaviour with them. The ex also seems to think it's because he is struggling being apart from them so he is acting out, yet when he is here he is fine, doesn't cry for them etc, unless I tell him off, than he may have a moment where he goes "want 'other parent'" but that's not a regular occurrence. Surely if it was because he was struggling being away from them he would be a nightmare for me because he would just want to be with them and he would constantly be asking for them etc? I tried to say maybe it's because Monday and Tuesday he does pretty long days (6.30am - 7pm) and majority of that he is at nursery (the ex works there also) and the nursery has been pretty crap lately, inconsistent with staff etc and he hasn't been enjoying it like usual.. so obviously come Wednesday he is exhausted and emotional.. but obviously the ex doesn't think nursery is the reason.. and is adamant it's just because he is struggling with being away from them.. I feel like I'm banging my head against a brick wall because the ex isn't listening to anything I'm saying.. seems to think they know everything and what's causing him to act out with them and it feels almost as if they are blaming me for him being difficult with them.. with the bedtimes and saying how he says "don't want to go mummys house" etc yet he says exactly the same thing here but about them, saying he just wants to stay with me etc. Please let me know your views and anything that can be suggested or tried etc.