capture card and audio issue

[Kim_NT]

Hello I have a very annoying issue with audio and was hoping some one would know more about it.
I recently picked up an elgato HD60 S+ capture card to stream nintendo switch games on twitch but i have a problem i just can't figure out on my own.
The issue: I have 2 monitors right now. The second one i use for obs/discord and stuff you don't want to see on stream (background stuff) This second monitor only have 1 hdmi port.
Then i have my main one i play the games on. The main monitor is plugged into my pc (display port) So that means the elgato goes into the second port of my main monitor (hdmi1)
I start the switch and the game shows up on the elgato software just fine The only issue is the delay from when i press a button and when it shows on the capture software. So the delay is a problem for me..
to fix the delay i changed my main monitor from input 1 (display port) to input 2 (hdmi) To play "directly" off the switch instead of using the capture software screen. That fix the delay issue, but brings me a new problem. Sound..

On input 1 (displayport) I get audio from my desktop that's easy to balance. But if i use the input 2 (hdmi) It forces me to use sound from the elgato card for my game instead of desktop audio. 
So that makes a mess of my audio balancing for example discord and such needs to be turned down to like 5. While the elgato audio needs to be around 70. So i can barely hear any sound from my desktop and on the stream. while the game audio in my headphones is super loud compared to everything else.  So wall of text later.. What i want is the input 2 of my main mintor (hdmi) to use the desktop audio from input 1. Can a splitter or something do that?  

[ShearMe]

...huh?