Flossy; the custodial parent need nit report everything, but surely, if a child had suffered an accident in the last day or so, that warranted ongoing attention, custodial parent would mention it. I know I did, though the one time it actually mattered, step-mom (a nurse!) didnt mention it to their dad. By the time her shift had her at home and attentively bathing the children, wound had gone septic. But by golly, I had told the adult I left them with!
If he won't agree to anything you have suggested, the next step is to have the court involved. The court can review his medical records and make a ruling, without you invading his privacy by seeing the records yourself. If his condition truly is not problematic, he can prove it in court.
Put it in writing:
dear STBXK,
In response to what I know of your ongoing issues, and in response to (situations i feel I should have been alerted to), I have suggested Plan X, Y, or Z. Your lack of cooperation has resulted in incidents A, B & C. I am open to any formal incident tracking plan you would suggest to alert me, in writing, to any accidents that might happen to the children while in your care. Naturally, i will use the same system to inform you of such incidents as may occur in the day(s) preceding your contact which may need on-going attention.
If we cannot come up with a workable plan, we shall have to ask the court to provide a solution.
Sincerely,
STBXW