But ghostspirit, this is your daughter's boyfriend, her relationship. Somehow you're blurring the lines, even if you think you aren't. My then boyfriend moved in with me (at home) when I was 17 and it started off the way you've described it, a few nights here and there and then it became, "Well he might as well move in". It was a disaster.
If you move him in then number 1, you're undermining his parents. Have you even met them? Spoken to them? Know them at all? I know that my boyfriend at the time hugely exaggerated parental misery and it skewed the picture somewhat. He was also 'under my feet' at home all the time and we had no time apart. That really wasn't healthy and, this was what I wanted at the time... 
Have you even spoken to your daughter about your concerns about her boyfriend? She is your number one priority, not this chap. It sounds to me as if you're going into 'mummy mode' - and I mean that very kindly indeed but he is not your child and I really think you would do very well to take a giant step back from 'interfering'.
If you really think that he needs TLC then invite him to meals when he's at your home, let him be a very welcome guest BUT... do not make him one of the family because he isn't. If/when your daughter moves on from him (and you say yourself that she's young still), you will have to distance from him. How are you going to do that when you've practically adopted him? Think about it now and you won't be posting back here at that point saying "How do I ask him to leave?".
How about meeting his parents, expressing your concerns to them instead of taking everything on face value? You may well find that the picture painted is not quite - or at all - as it's been painted. At least you'll know and you'll know how much/how little to do from that point on.
At the moment, ghostspirit, I think you're being a bit of a mug and I would really like to know what your daughter thinks of all this. At the very least, stop giving him money and stop buying him 'things'... it's not your job and it could be very unkindly misconstrued.