Fair enough but isn't pace going to be a problem no matter where you play him? I'm not an expert at this game but let me give you my reasoning and I welcome constructive criticism.
I don't think he can play back, his pace isn't the only physical problem, his agility isn't much better plus that bravery attribute of 2 worries me. The OP is thinking of making him a playmaker. I wouldn't waste the training time on that, his flair rating is 5, his finishing isn't great either and he needs to be trained on creativity and flair, and pace and agility would still be an issue.
I know he can't play as a winger, even with training I'm not confident he'll ever be fast enough and good enough with the ball at his feet to consistently beat his opponenet and put crosses in, and he's just not an attacking player.
Central midfield. He's not a playmaker or a runner because once again pace is an issue. He's not a destroyer. He has bravery of 2 and is also only 5'7" and can't jump. I think he'll be a liability no matter where he plays in the central midfield.
Wide midfield I think he can play because in order to play there his attribute increases don't need to be as extreme as they would have to be to make this kid a playmaker. As a wide mid he doesn't need to be explosive like a winger and he'll have help on the flank defensively from the fullback. With a reasonable increase in flair he should be able to make some nice crosses and passes and he already has the technical skills.
He's 18 which sounds young but I don't think he is. He has a lot of physical training to do, his pace, agility and jumping all need work so every moment spent on that is a moment not spent on training other parts of his game which is why I think it's a waste of time to try to turn his weakest attributes into strengths. I'd personally spend the time on attributes that are a little higher like corners, long shots and free kicks.
With the necessary increase in speed I see a wide midfielder who might also be a decent set piece guy. Like I said, I'm not great at this game and I welcome constructive criticism so I can get better at this but I don't see a playmaker or a central midfielder here.