ok so i would keep the downscale you have for fps sake because streaming in 1080 is useless on twitch. even though you have a fantastic upload the max bitrate i would use is 3500 because over that some viewers have trouble watching. if you get partnered u can go higher but since your probably not dont go over 3500. i would put the buffer at double the bit. quality at 7 if your doing fps games and at 8 or 10 for mobas. audio bit at 128 is fine but because ur internet is awesome you can go higher if you please. you should be good with these settings let me know how it goes.