OK, this is the time for YOU to be strong, and for YOU to demand more for your life and your DS.
YOU make the decision that he is GONE, that HE doesn't get to call the shots in your life when he not only contributes so little to it, he actually drains the very soul out of it.
How could being single be any worse than being with a waste of space like him? seriously? How could you genuinely introduce this bloke to anyone you value with any pride at all?
When the question What does he do comes up, The Answer? as little as possible, but spends money like water, steals money, lies and sits on his arse all day?
HE has failed YOU. He chooses not to provide for you, and worse to make life harder by lying and stealing money from you. Your parents kindly saving your blushes, but they are enabling his shitty behaviour. Really it'd be kinder for them to read him the riot act.
You are standing at the cross roads in your life - one path leads on from the path you have been on, all down hill, deeper and deeper into the valley, the other leads away from all this, uphill, harder to walk to begin with, but when you get a far way along, the view is amazing.
He can choose to walk with you, but he has to realise that he has to put in a lot of leg work, or you will keep going without him. The path that man is on, offers ZERO hope, ZERO improvement, only further disappointment and sadness.
Without him your life actually has hope and prospects. With him, not so much.
Can you see that? Cos it's glaringly obvious from here.
If your parents are so helpful, then they will continue to help you, perhaps more so. Have you spoken to them about this?