Does the Blackguard poison weapon ability increase with levels?

Does the Blackguard poison weapon ability increase in strength or number of time it can be used per day with higher levels (as the assassin ability does) or does it remain the same throughout the game? The description is not clear.
Also the description says that it "deals an extra 2 points of damage per second with no saving through (for a maximum of 12 points damage" and that "if the target fails a saving throw... he will suffer an extra 1 point of damage for 4 seconds there after".
Does that mean that in the first 6 rounds after a hit the damage would be 2 HP per round, then a further 1 point per round if the save is failed?
Also the description says that it "deals an extra 2 points of damage per second with no saving through (for a maximum of 12 points damage" and that "if the target fails a saving throw... he will suffer an extra 1 point of damage for 4 seconds there after".
Does that mean that in the first 6 rounds after a hit the damage would be 2 HP per round, then a further 1 point per round if the save is failed?
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Comments
It is just that, 2 dmg/sec until 12 dmg and then 1/round for 4 rounds if the save is failed.
It basically destroys any spell casting attempt for the time.