In the screenshot you sent me on Discord
in the top right corner you can clearly see that your game is in fact using your dedicated GPU where it says "Display: AMD Radeon R9 380 Series".
What you are asking in this thread is to run the game entirely off the Graphics Card so that it will use less Processing power and help your stream run better, this is quite frankly impossible as games require processing and graphics to run, you can't run a game entirely off of a GPU, it just doesn't work like that.
What you actually need is a new processor. (based on the information you gave me in Discord.)