Servers cost a decent amount of money and it would be a bit more work for the staff. I'd rather have 2 full servers then a third server with 30 people also. However as long as it was populated decently I wouldn't be opposed.
No way, just try and do your best to isolate the people you have in custody to avoid them being shot. Things happen, people get caught in crossfire, shot out of a car etc. The invincible cuffs would be a little overboard in my opinion. If it's clearly obvious they killed the restrained players intentionally report it.
Its because of the recent teamspeak update, mass mover is broken as well. You can look for other plugins but it might be easier to wait for the updated version