In rewards section of Final Sanction it states that the players get 300xp for each Primary Mission Objective met. But for renown it states "All Primary Objective complete: 1point." Does that mean that if they completed both Primary Missions they only get one point? If they failed one, would they then get no points? Or do they get one per Primary Objective complete? Thanks.

Well I'd have to say, its if all of the primaries are met you get only 1 renown.

Reasoning: Your primaries are the things you must do to succeed in the mission, and all of those objectives are part of only a single mission. If you fail to complete a primary objective, you've failed your mission, and should get no renown. Other space marines aren't going to think better of you if you've failed.