How to map a community map and what restrictions do I have?

I want to make a custom insurgent wacky races/mad max type map.

First of all how do I get started in making the map? What tools do I need?

Second. What kit/damage values can I modify? Can I customize the kits?

Third. Would it be possible for me to base my map in co-op mode, but not have any cpu/bot players?