Does the Quest 1 just not have enough grunt to stream multiple monitors?
Given that a FullHD monitor needs to basically fill your field of view in order for text to be legible on a Quest 1, could you split the available frame-rate between the two, depending on which monitor is being looked at right now? Start with 60fps, split evenly between all of the visible monitors, so if you're looking directly at monitor 1, it gets say, 58-59fps, and the other monitors in the corner of your eye get 1fps each.