I'm sorry OP, but I don't really understand what you mean by 'i know what I need to do but my esteem is so low that it’s like I am settling for less'.
What do you think that you 'need to do?'
You certainly don't NEED to move in with this man, unless you want to, and are prepared to be booted out by his step children so that they can cash in when he dies.
In my opinion you do NEED to learn to value yourself! Tell him that if he doesn't appreciate you enough to marry you, then the relationship is over, and don't settle for anything less. We all want to be valued and loved OP, and if it's too much for this man who claims to love you and want to live with you, to actually marry you, then he doesn't value or appreciate you in the way he should.
Find someone who will treat you better, or stay on your own, indulge yourself by doing the things that YOU want to do with your life, and treat yourself the way you would like to be treated by someone else. If you don't value yourself, no one else will, but learn to love yourself and be confident in your own skin, and you might just find that your new found, shining self confidence, lights you up and gets you noticed by someone who will treat you right and appreciate you. Don't settle for second best OP, you're worth more than that!