Honestly, a bit ESH. The temp was out of line shoving everything on the floor. I can understand being upset by misgendering, but it doesn't warrant an immediate tantrum. Even if you were a hateful douche about it it doesn't mean they should ruin the coffee and doughnuts for everyone.
I don't think you were wrong to say dude. Unless you really emphasize the "dude" I think it's a perfectly casual way to address people. Modern usage has it shifting more towards "cool person" instead of just "cool guy".
I do think the "nobody cares" part was a bit insensitive though. I don't know where you are, but tensions in North America are high right now regarding trans rights (not saying this person was trans, as there's not enough info in the story). Lots of people care a whole lot more than they should about other people's chosen gender expression, so it's a touchy subject. I can understand that maybe you were coming from a place of "I don't mind one way or the other", but I don't think that's what it sounded like in the context. Especially with the "stupid" part thrown in.
I'm playing the ninja platformer N++. I'm probably not good enough to 100% it, but I'm having a blast with it.