The bottom line is, this is not going to get sorted out until both you and your Dh get on the same page and deal with it together. So far that's not happening.
The fundamental question that I haven't seen answered is, why is your husband changing his days? Is it, as various posters are posing it on his behalf, due to work requirements, or is it that he is being a selfish arse and doing what he damn well pleasies regardless of his family? If it's the second you are absolutely NBU, and if it's the first he needs to negotiate that with you up front.
The second question is, does your DH keep a low profile during the day, or does he swan out whenever he wants to, play Disney Dad for five minutes while the kettle boils, then swan off again leaving you to deal with the inevitable meltdown? I'm sure there are ways of him not being present/ visible in the garden building for a start, and he can park his car round the corner.
These are fundamental questions and the answers will be illuminating for us all in what's really happening and how best to deal with it.
Another thought that strikes is that tantrums in 2/3 year olds are pretty par for the course, they are tough, but as a parent you need to start getting used to saying no and meaning it. That goes for both of you, not just you. Never let a child play one of you off against another, they are adept at it if they sense an opening.
So many questions are still unanswered, but yes you absolutely could deal with this if you both posed a united front.
I'm afraid this is only the start of it, it's only going to be tougher when he's six feet tall.