'if you cant keep up with your chores you wont have a job outside this house' and 'You're only sixteen, you don't even need a job.'

No. This is not okay.

If you're putting up with this bullshit, seek help. If you go to a school, tell them about it. I know exactly what you're thinking as you read this, "No, it's not that bad, it's just Mom being a dick," and you're fucking wrong. You have a right to go outside and have a job, and the fact that you're made to do a significantly large amount of chores even for someone without any form of arthritis is completely unfair, not to even mention that you receive no praise from her.

I've had similar, manipulative problems with a stepdad who's fortunately out of my life now (although, to say the least, he didn't leave in the most pleasant way), who was essentially nothing more than an alcoholic asshat who felt like he had total control over my entire family. And even after he left my life, he still affects me to this day. I was never allowed to go out of the house and socialise with my friends (while I had them), and the constant fear of going back home to him without my brother or mom was seriously affecting my social skills and I'm still rather awkward today. People also notice how nervous and flinch-y I can constantly be, and sometimes it can get it the way of what I'm doing - while he fortunately did nothing to me, that isn't true for the whole family, and even before anything escalated to that level the consistant arguments that occurred every night between mom and drunken stepdad were enough to put me on edge.

I didn't even understand how bad it was until a month or two ago (he's been gone for two or three years now), and until then I assumed it only barely scraped into the domestic abuse category. I actually made up things about it to make it seem worse to some of the people I told, because I thought that if I said things how they were, they'd see it as nothing bad and merely shrug it off, not giving me the sympathy I needed.

While I regret a lot of things I did and didn't do during the time he was here, the one thing I'll truly never forgive myself for is not saying anything to anyone who can help - because I know very well that I'm not the only one who suffered because of this.

This might have turned into a more "i need to get this off my chest" thing, and if it did, I'm sorry, I've never got into this much depth about the situation before, and it's something I really should just dump into a big rant, even if it's to a random stranger. But, please, do something about it.

TL;DR: Tell your school or anyone who can (or can't - chances are they can help you find someone who can help, and even then it's best to tell someone in person than keep it locked away) help with the situation to end it before it ends much less peacefully. Don't make the mistake that I did, and make you and your siblings suffer for it.