There is nothing you can do unless you connect the display to 8 GB or 6 GB card. As this isn't possible in your case, you can instead run separate instance of PhoenixMiner for just GPU1 (adding the argument -gpus 1) and use a pool that only mines ETH. The other five cards will run on another instance of PhoenixMiner (with -gpus 23456), that can mine both ETH and ETC.
How to make this? With a 2 bat files? I will have 2 miners on the screen or is it possible to make in one?
No. Create one config1.txt for the first instance and one config2.txt for the second instance. Start first instance with ... -config config1.txt ... . Start the second instance with ... -config config2.txt ...