As for the "difficult to read" part... I agree with PeaceBaby's ESTJ in that we're actually not so hard to read. What you see is what you get. So if you're confused by why he acts happy one moment and then acts like a d-bag the next, it's that his emotions vary that much. He's probably not putting on an act, or trying to be manipulative.
That's probably just bad timing. I agree with PeaceBaby's ESTJ here too, in that he wouldn't talk to you if he thought it would get in your way. In a sense, the fact that he chats with you at all means that he trusts that it won't get in the way of your work, and that you'll still be able to get it done.Anyways, when he's in a good mood and wants to chit chat, he expects people to talk to him about whatever (sometimes lame) subject that he's talking about. Usually, I'm not interested in what he's talking about. I'd rather just be left alone and do my work. I wish he could see that and appreciate that. But, then later, when he doesn't look busy I might try to talk to him just so that he knows I'm sociable and somewhat friendly (not because I feel like talking to him) and then he won't want to talk.
1. He doesn't hate you, I'm pretty sure. Nothing you've described sounds like hate OR disrespect, to me.What's the best thing one of your employees/co-workers could do to at least get some of your respect? Is it OK to just shut up 90% of the time and do my work or is he going to think I'm a prude? When I stay quiet and just focus on my work, it's like he thinks I need something to talk about. I don't. I just want to work. Besides, we don't have much to talk about anyways. He doesn't want to talk about things I want to talk about and vice versa. We don't have the same interests at all. But, I don't want him to hate me for crying out loud.
2. If your main focus is to get the job done, and you show him that without pretending to care about him and his personal life/interests, he may think you're humorless and cold, but he will still respect you. In fact, he may respect you even more, for being so focused.
1. Nitpicking is NOT the same as disrespect, with ESTJs. I'm 99% sure that he respects you. If he's like me, he'd be very cold and completely unfriendly/distant/uncommunicative/one-word-responses with you if he didn't respect you. (It would be very obvious.) It looks like you associate friendliness with respect and vice versa, but that's not how it works for ESTJs at all. Just because they consider themselves to be right unless proven otherwise (which most people do, anyways), doesn't mean they consider themselves to be better than you, or that they consider you to be unworthy, or anything like that.
2. The nitpicking is just his way of making sure that everything works out okay. Often when he nitpicks, and saying things like "Why are you doing _____?", he's not asking a rhetorical question, and is genuinely asking you why you're doing that. So, here's the code-breaking:
"Why are you facing the wrong way?" = "I don't understand why you're facing that way. It doesn't make sense to me. Prove me wrong. Make your case!" So, even though I doubt that he'll stop doing that, it should at least help a little bit, if, unless you're doing this already, you make your case to him every time he nitpicks, in a cordial but firm way.
I understand why it would be so infuriating - I mean, you guys are speaking completely different languages - and even though I can't think of a way that you could get him to change his behavior, it should be of at least some comfort that I'm 100% sure that he likes you and respects you AND the work you do. The mixed message he's sending are due to the fact that ESTJs have pretty much no Fe, so when he isn't in a really good mood, he's not going to pretend like he is. It's not "Be nice or mean - pick one", because ESTJs don't work that way.
Sorry I couldn't help more.