Schools must be dead accommodating where you are, or maybe it's post-Covid, but in 21 years of primary and post-primary schools, parent-teacher meetings were held during the teaching day.
Anyway @Buddythecat1 those days ought to have been annual leave not parental leave. I'd never have used a precious day's leave for a child's birthday though; maybe half a day if they were having a party, maximum - and you have 4 to accommodate.
I think you could write formally requesting that those parental leave days revert to annual leave. It's perfectly reasonable to outline commitments during a recruitment process. That would cut down the number of days' absence. I'd take that opportunity to set out the fact that you are entitled to breaks that you're actively being denied. That's dreadful that you are forced to eat in the toilet! I had to hide my inoffensive, non smelly sandwich in a drawer for a year and a half, making sure the coast was clear so I could open the drawer and take a bite, without toxic manager seeing me as she had forbidden me to eat at my desk (yes, just me!)
What exactly are they "investigating" anyway? How do they think they could ever 'prove' you weren't ill when you say you were? Nonsense. They are thick as well as toxic!
I imagine the sick pay scheme will be pretty shite as well. All sounds very dodgy but unfortunately you don't have the service to take them on. However you might be able to delay things while you jobhunt if you are signed off with work-related stress. Legally they have to at least take you through a "three step process" to terminate your employment, and you could prolong that process by saying that you are not well enough to attend meetings. It wouldn't be a lie either - you're stressed to the eyeballs!
There are some total idiots of posters on this thread too - don't let them get to you. I've been bullied, and that's what's happening to you. The micromanaging and constant, unreasonable fault finding grinds you right down when it's happening on a daily basis.
Very best of luck with your interview! When you do leave the shithole, make sure you have an exit interview with someone more senior than your managers, and tell them exactly why you're leaving!