A302: As written, there is no added cost, but if the enhance talent requires a spell point then that cost still applies. Concentration is not needed. The ability works just like normal casting, except as stated otherwise (i.e. swift action to cast, limited to the Sage's reach, and duration is [wis mod] rounds instead of any other duration).
A303: As written, yes. "For every 4 class levels the sage possesses, he gains one [esotery based] talent as a bonus talent." The wording doesn't say you receive them at levels 4, 8, 12, etc., it says you receive them based on how many class levels you possess.