The code listed below should be able to do 3/4 of the things asked.
# Events
chat:
set {_fc} to first character of message
{_fc} = ">"
set chat format to "<%player%> &a%message%"
command:
command contains ":":
player doesn't have permission "*":
cancel event
send "&4Illegal syntax!"
command:
command = "/me", "/say", "/help", "/?", "/version", "/ver", "/plugins" or "/pl":
player doesn't have permission "*":
send "&4No permission!"
To make players spawn in a radius around spawn rather than directly on it, you can use in-game gamerule commands. To do this, type in /gamerule spawnRadius. You should be able to fill in the blanks from there.