Just to elaborate a little more on what Trilir said..
1. Typically "bots" are used by melee classes. The "bot" is run by the same player as the the other class and its main purpose is to fully buff the player without losing exp to a group.
2. If, like you say, you were spec-ed to 20 and the mace gave you +2 spec your spells would have the power of a level 22 cleric's spells instead of a level 20's. However, you would not be able to use a spell that you get at level 22, all of the advantages are not shown, they are just in a formula that figures out damage and such.
3. As I play a sorc, I am the "crack dealer". Usually "crack" is referred to as a spell that sorcerers have that help the mana regeneration of a caster class. However crack can also just simply be mana itself.
Hope this helps :)
Good luck!