I also worry about what this is making me become at times (bossy, manipulative, a liar, cross) and hearing myself being this way is horrible. But I know in my heart this isn't me, just as I'm sure it isn't you. You're not going to change fundamentally from the decent, nice person I'm sure you've been all your life, and we just can't beat ourselves up for what this dreadful situation does to us from time to time - absolutely no one, no one, could cope with this without cracking sometimes.
If it's possible to be in a different room for a while after things happen that make you feel this way, I find it can help a bit - getting him to go upstairs was a good thing to do.