Narcissists will often accuse others of being a narcissist. It's called gaslighting. You didn't do anything wrong. Your bf sounds like an entitled a$$ hole and a user/loser. His kids are taking after him.

 if I am not "all about his kids" meaning if I don't plan my entire life around him and his kids and all of my free time around what they want to do ....

 perhaps I am not cut out to be a step parent

You are dating now and he's expecting you to revolve around his kids. This is the part of dating when he is at his best. Do you really want to stick around and see how it is with this guy, who can't manage money, when he is not at his best? If you do, get ready for the if you loved me and the kids you'd pay gaslighting.

First you aren't a narcissist. Not even close. Do not under any circumstances allow him to call you names like this or devalue you anymore. Second your bf is looking for an instamom. Men like this are extremely self centered and expect a robot doormat type of woman to drop everything and cater to them and their kids. Do not do this. This is not a healthy life for anyone, including even those with the lowest self esteem. He needs to get his act together financially before he seeks out a relationship. Otherwise all he will find are the low hanging fruit types with low self worth who have little going for them. An attractive, financially stable, intelligent woman with a good career will want nothing to do with a man like this long term. Maybe just fun and dating until she sees the red flags then out the door she will go. Also please quit paying for him and his kids!

He's irresponsible with money and verbally abuses you for disengaging. What he actually means is that he needs you to behave so he can use you financially. You won't love him for much longer I think.

Oh gosh I didn't even plan my own life around my own bio kid. Sure, I made sure she was fed and safe and loved, but my every waking moment was not devoted to her.

Engaging in namecalling is juvenile and designed to make you feel bad so that you fall in line with what HE wants. He'd love it if you were Replacement Mom when he had his kids. And he'll continue to be financially irresponsible as long as somebody is willing to pay his way.

He sounds immature, at best. Controlling with an anger problem more likely (yelling at you because you went for a walk? Seriously?)

What are you getting out of this relationship that makes it worth staying?

Girl throw this one back. He does not sound like a good catch at all! 

It is not that your not cut out to be a step-mom, it is that your SO is not cut out to have a girl friend. He sounds controlling and angry. You are doing nothing wrong and nothing that most step parents would not do in a healthy relationship. You can do better. Please take what you have learned from this relationship and move on.

And get the puck out of there. Its not that you are being accused of being a narc - your REAL problem is he is devaluing you and using you.

You did/do everything right - you keep yourself to yourself, have a career, have your own friends, are active in healthy pursuits, are not trying to discipline the brattys, take yourself out of situations rather than create conflict, are not trying to be mom/replace mom.

The only thing you are doing wrong is not using paragraphs in this post!

I understand that he seems great right now, but this is the honeymoon period.

Id definitely read up on this site!

He is not a nice guy. At all.

Let's see: 

He yelled at you for going for a walk..

He gets you to pay for him and his kids

Expects your life and every spare moment to revolve around them 

Calls you names 

Wants to control you. 

You can do better, so much better. You don't need a man to fulfill your life. You have yourself sorted.

Please don't get sucked in or dragged down by this guy.

Run for the hills. Let's see, you are doing everything right, focusing on your career, bettering yourself, taking care of your health and fitness, spending time with your good friends, keeping to yourself, minding your business and are living a healthy life. Don't ruin it by becoming an instamom, stepping where you don't belong when the kids have a mom, disciplining or enabling poorly behaved brats who aren't yours, getting involved with a user of a man who is not only mean to you but also irresponsible with money. Ever wonder why he is divorced with kids? Now you know the answer. Karma has a way of coming full circle. Create your own happy healthy karma, not toxicity, drama and vindictiveness. He is not the one luv. Hugs!

Others have already made good points about this man - ie if he is treating you like this, at this stage, things are only going to get worse if you were to move in with him etc.  You only did what any reasonable person might do - this does NOT make you a narcissist.  He is obviously not a very good parent, or potential life partner - I'd ditch him.  

He expects you to be a replacement mummy to his kids??

frankly skids being rude, disrespectful, centre of attention etc will not have me like them one bit. Your life does not revolve around his kids. Frankly from what you've said, he's treating you more of a nanny to take on the kids so he doesn't have to do the job of raising them.

if he wants you to spend more time with them, he can at least make his kids respectful and pleasant when you are there and parent his kids.

It doesn't matter how much you love him, it will never be enough to make up for all the crap he's feeding you. He wants a stepford mommy who worships and runs after him and his kids. You want a normal life. Square peg, meet round hole. 

This one's a dud, throw him back. Chalk this up to experience. 

What the hell are you doing with this gaslighting dickhead and his shallow and polluted gene pool?

Save yourself a lot of pain and move on.

NOW!