1: Current level cap is 20.
2: Farming would be best done in /join ingiru or /join deathitude Currently there is no war or event area, but those would also be good places to farm.
3: Warrior spirit has since gone rare, but is still a good buff. Adding Super Speed would be a good idea, and the Elastic abilities in /join herospire and /join skulldeep would be amazing additions to physical builds as they have very short Cool down phases for fair damage. Episkea is a good heal skill, but Focus is almost adequately replaced by Warrior Spirit.
@axell5: A BEST skill is almost impossible to name. It really depends on personal preferences, but the Legendary Powers can be earned from PvPing extensively, and they are all good. Also, Plasma Net and Chuddling Rush are both OP at the moment, making them very appealing.
@dra suzumebachi: To go one step further: Here is the Wiki.