I would keep him isolated. If he is contagious then it would be a disaster to introduce him to another flock of chicks. Again, expert advice would be helpful, but if a chicken is laying down, I think something serious is wrong.
Oh, and I just noticed you posted this in a regular thread. Please...
If he's falling over, then I suspect that is not caused by loneliness. Do you have any Rooster Booster or other vitamin stuff to put in his water? It sounds serious to me. Experts will chime in, but I'd do a full examination. Check his crop, breath, vent, et al. I have heard that they shake...