Sounds like he's using that as an excuse to NOT marry.

Dont marry him. Find someone else. Avoid a lifetime of comparing stephells on this website. You can do better. We all could have. 

You can do better. 

If he makes an ultimatum like that, you can too. You can say "Look I'm sick of shacking up and want to get married and do x, y, z . - and if you're not willing to do that, then it's time for us to move on separately."

Nope. You are stepmom at best not her parent. You need nothing more than to be her friend. Which it sounds like you are. He is using it as an excuse to not marry you. Also, don’t be with someone with kids. She may have a decent relations with you now but that will change. Don’t ruin your life the way we have. 

Your BF's expectations are not realistic. Don't waste another minute waiting for this guy to decide you're sucking up to his daughter enough to be "good enough" to marry him.  He doesn't value you enough. Leave him so you can find someone who does.

SP can never fit the perfect family role. You can never love this kid as your own. Because she is not your own. He will never have children with you, because he knows once you have a child. SD will become second, That just the way of life. And he know that.  He had his chance for the Happy Family with BM, we see how that went, He can not recreate some thing that was never WAS  

Run, Run,  start over with some one else. 

What does he want from you, exactly?

I'd be very put off by his "demands" of what he needs for you to do in order to get married. He either wants to marry you, or he doesn't want to marry you - sounds like he doesn't, but he's willing to live with you.  If he doesn't feel you are good to his daughter, why is he OK with living with you? What exactly does he see changing when you are married, except that it's harder to end it?
 

To me, this is like him saying he needs you to lose 40 lbs, or build up more money, or get a better job, or whatever - before he will marry you.   I agree with someone above who said he is using this as an excuse not to get married at all.  And the idea that you have to jump through hoops for him to agree to marry you is really offensive, to me, anyway.

As hard as it will be, might be time to move on.  Find someone who wants to marry you just as you are.

Girl, why are you settling for so little? Its past time you moved on and stopped hoping for this guy to begrudgingly marry you. Find a man who is crazy about you! One who is willing to cherish you, fight for you, and can't wait to put a ring on it.

Every woman deserves to be romanced and courted. I'm well into the third decade of my marriage, and despite his imperfections, my DH treats me like a queen. Shed this dude and all his baggage, and find your prince!

 My BF explicity says that we are not getting married until I consider us a family and make more of a commitment to better my relationship with her

There is no way that you are ever going to meet his standard. Even bio parents have rough relationships with teens. What he's actually saying is that he's just not that into you. 

Take him at his word. Your choice is to leave and find a guy who is into you. Or to stay and wait until he finds someone who his is into and be told to leave. 

My relationship with my husband has NEVER had anything to do with my relationship with his daughter. As long as I did not mistreat her, there was never a prerequisite that I be committed to her, in order for him and I to commit to each other.

I call bullshit.

Rejects any effort from you being polite and civil and to start a conversation. What then? Is your boyfriend going to not propose because apparently you relationship isn’t close?

My almost 21 yr old ss ignores me and our 2 toddlers (his half siblings), he goes out of his way to make sure we know we don’t exist in his life but he pretends that he likes us when in laws are around.

My kids don’t have a sibling relationship with him, heck even hubby doesn’t have a proper relationship with him due to pas.... hubby doesn’t make me parent his kid, he simply said since he’s at work all day and i know whats going on at home if there are issues i am free to tell skid off like when he dumps trash on kitchen floor because he was too lazy to empty it..

I refuse to do this and put it on hubby to address it so i will message hubby to address it as this is his son he needs to parent.

His daughters are no better, they have the same pas their bother has but even worser they do everything bio mum says even if inappropriate and they justify it. Being civil, caring for our home and hubby should be enough for him to accept me in marriage.

It seems op boyfriend here has the mentality of “love my kid like your own” thats just not realistic

If he loved you and wanted a future with you there would not be a condition attached: you'd already be married and dealing with family life as it comes. 

He should consider himself extremely lucky that you and his daughter actually get on.

Either he's scared to get married or he wants to continue using you for the comfort you bring to his life. 

He gave  you an ultimatum.  I do not tolerate ultimatums.  Call the locksmith, re-key the locks, and put he, his ultimatum, and his toxic spawn on the curb.

If he wants you to have a better relationship with his prior relationship breeding experiment he needs to up his parenting game and mold her into a person worth having a relationship with. His failures as a parent are not your problem. 

Write this shallow and polluted gene pool off and move on with your life.  5yrs is far too much of your life to have wasted on this prick.

Ultimatum my ass!