50/50 shared care - I receive child support $ - who pays for what?

So my ex husband and I have four daughters, three of which are still deemed dependents. The eldest lives with me full time and the dependent 3 spend week on/ week off between my ex and myself. Unfortunately, 12 months ago my had to cease work, which has rendered me not only mentally devastated but financially also. Since we separated some 6 years ago our relationship has been mostly amicable, except when it comes to money. My stance has always been that when it comes to expenses for our children, costs should be split 50/50 - so essential items such as items needed for schooling or their healthcare. Anything else is up to the individual to decide upon - which basically means I am, and have always been, the one to pay for their clothes, shoes and other incidentals. Due to my current situation I am now receiving a disability pension and my ex is required to pay child support, which he does so begrudgingly each week. Two of our children are currently in therapy, which he is in support of, so long as he doesn’t have to pay - he believes that they can just get the free support (which is not equipped nor staffed with the professional support that our children need). I contacted CSA who advised that I can make a claim which they will review, but advised that this is something that would not necessarily be covered by his current payments to me. I haven’t pursued this as I just don’t want to deal with the drama it will cause with him, and the onslaught that will ensue (such as delaying making his current payments) However, I am just wanting to know what are the expectations or experiences of others in similar situations when it comes to expenses when the care of the children is split 50/50? Who pays for what and what expenses are split and not deemed to be covered by the child support payments you pay or receive? I’m just so confused and annoyed by all of this, and hate that I feel like I have to constantly nag him to get him to pay a share of what I am forking out for OUR children. Let it be noted that I did not choose to be in my current situation, I had previously held a position at work which paid well and allowed me the luxury of not having to rely on money from anyone else. (Okay since starting to write this I jumped on our old mate Google and have delved a bit deeper into this and had a few questions answered - but has led me to also want to know this now - is it the responsibility of the person deemed to be the “primary carer” and recipient of the child support payments to purchase and fund all things related to the children’s schooling? Whilst I understand that payments are expected to cover these costs, how is this managed/coordinated in other people’s experiences? Thanks so much in advance for any insight you can provide