Skye, I have absolutely no advice for you. Just wanted to send you lots of hugs. It sounds like you're having a really rough time and trying your hardest to do the right thing. I think it is very brave of you to be so honest and I definitely can't blame you for feeling some resentment to your challenging toddler. Hey, I have a beautiful head strong one year old and although most of the time I love her so much that it hurts, sometimes I feel some resentment towards her. She just really pushes my buttons. And when sleep deprivation is added to the mix, it can get challenging. Now you have 3 kids and one that is definitely a handful. So no wonder that you feel the way you feel.
I hope that you can find help with your situation. But it sounds like some of the ladies have already given you heaps of good advice.
Love, Sasa