Scaled render texture misaligning mouse movement

I’m using a render texture on a quad to make my game camera display a specific height/width of pixels, to be viewed scaled up for enlarged perfect pixel screen sizing.

To do this I’m putting a render texture on my main camera, setting that texture size to half the size of my target resolution, and then using another camera at a higher depth to show the quad it targets.

This works great, however, my mouse position appears to be scaling along with with the rendered texture, syncing at the bottom left, but moving farther away outward from it. I need it to stay synced on the main camera so I can click, hover and raycast. If anyone knows why this is happening and a way around it, or a way to set the camera facing the quad to be the main camera but translate mouse input to the camera rendering the gameplay, that would be great. Thanks!