The bis_weaponpack error is common, annoying, but fortunately not serious. There is a good thread on it over on the official forums. I can't remember the details but it appears, for example, when you have a weapon in Gear selection but not in the mission: the addon name is therefore not in the mission.sqm and the error is generated. The fix is to add the addon manually to the mission.sqm.
However nominesine is right, it may be that you need to DELETE bis_weaponpack from your mission.sqm. ;D Welcome to the crazy world of mission editing. Don't forget to check the Intro and Outro sections of the mission.sqm.