oh gosh i feel for you--
first, my guess? yes, he is drinking... and frankly even if he isn't, his behavior is petulant, juvenile, selfish, irresponsible and blaming so he might be sober (though i doubt it) but he is still behaving quite alcoholically.
do you have any family or friends around? i ask bc i decided (way too late mind you) not to ask stbxah to help anymore (now he can't bc of a RO but before that i mean).
for ex/ i might call and say child is sick, can you help tomorrow. if he says yes, leave it at that, don't remind, call again, or depend on him showing up. make a back up plan so that YOU are in control. that way if he shows when he is expected, great and if not, you can calmly go to plan b.
i told stbxah probably 7-8 months ago that if he agreed to do something (helping with the girls primarily) and said he'd be there at X time, that that was my expectation. and i added that if he was more than 5 min late, i'd go with plan b and he needn't bother to show up.
result? he showed up on time a few times to help and then tried to not show when he promised and come late and i made sure i was ready to leave to go with plan b and followed through. he got very angry (just to forwarn you) but the relief of not anticipating "oh my god will he or won't he show up" was well worth the verbal diarreah he threw at me.
i know how hard it is as a teacher to have to cancel classes and it impacts a lot of people and i can imagine how upset you are. do you have a good r/s with your administrator bc it might be worth saying simply that your other half simply didn't show and letting your job know that it won't occur regularly and that you were as surprised as anyone that this happened...
so so sorry for all you are dealing with.
he will test your limits and push even more from this point on i am sure. try to have a plan b who you can depend on so that you don't have to be tied to an irresponsible jerk who can't be counted on.
xo