ok...not being funny here, but....what makes you so sure that none of your friends would be interested in him? Is this purely because of his size?
My husband is a big guy. Bigger than your friend. I'm nowhere near that size, I'm a size 16, but was a size 12 when I started going out with him (granted he weighed less then too though, he was maybe 22 stone or thereabouts at that point, but still, a big guy).
Just because a lot of girls aren't interested in somebody large, doesn't mean that he's never going to find somebody to love him.
I'd rather that my husband lost weight (and so would he, for that matter, he's getting a gastric sleeve done this year) for health reasons, and the fact that he is barely mobile is a real problem in our lives, but in terms of aesthetics, I love him anyway, because he's a nice person.
The more worrying element to your friend, I would say, is his strange behaviour regarding "falling in love" with women. That is very offputting.
In terms of his weight though, yes I agree a lot of people would be turned off, but it's not COMPLETELY unrealistic for him to think that somebody will fall for him one day, because it can and does happen you know. Bigger people aren't aliens. Somewhere out there I'm sure there's somebody for him. He could do with not trying so hard though in the "love" department, because that just comes across as slightly stalkerish and creepy.