Yeah, "solving puzzles". If that's the case, surely it can wait - why does it need to be solved at 2 am? Anyway, if you're gonna be a slave for $200k please go ahead, its yo choice.
On call typically means you gotta be online and respond within 15 minutes if paged. That's abusive. If you want a person to do that, then pay them for that. As an example, on call in Amazon works the way I described, and yes it is abusive.
Your second paragraph is spot on. When ever I login I see random sheet contents and equally sheet comments. Give me a resume hosting + job post/search site any day.