The labels are indeed only [0,1] [1,0] and [0.5,0.5], but I wouldn’t consider them discrete since [0.5,0.5] is not a class of its own but the equal presence of the other labels, which is why I think using 3 discrete values would be wrong in this case. The [0.5,0.5] labels are there to show the machine that both emotional states can be present resulting in neither being prevalent. I thought MSE was the best way to go about it, but I could totally be on the wrong here.
Also the sample distribution is fine with approximate the same number of data samples for each label.