I think it's great that he wants to learn! Just keep encouraging him, and let him know that it gets easier with practice.
Speaking of practice, he can learn to use the sewing machine by sewing on lined paper, with no thread in the machine at all. That will allow him to learn how to control where the stitching goes, without worrying about thread tangles etc.
My son (now 19) had made a pillow in life-skills class in 8th grade. Under my obsessive eye, he even did a fine job of the ruffled edge. I thought he'd forgotten how to sew entirely, until this summer when he took a fabric scrap and made a catnip-filled toy for our kitties to play with. Ok, so it was only a roughly sewn rectangle, but still, he thought of it himself and did remember how to use the machine!