1. Can I promote a halal product for commission if the seller’s site has haram content (women, music, false claims)? 2. is selling or promoting a product that can be used in both halal and haram way permissible? 3. Is game development halal if it may cause addiction among the users?

Promoting a site that carries tabarruj is not permissible even if the product you are promoting is halal. Selling what can be used either way varies from one product to another, so I need more details. As for developing games, the ruling follows what is in the game itself. If it contains something forbidden then it should be avoided, and any amusement that turns people away from the prayer and the remembrance of Allah is forbidden.