iMac Target Display mode with multiple monitors - imac keyboard stops working

Hi everyone, this is a bit of a strange thing I'm trying to accomplish so bear with me.

I have a mid 2011 27" iMac that is no longer powerful enough for what I need (I'm a video editor) but it has a beautiful monitor. So I've decided to use it in target display mode with a newer mac. That works everything is great. Now due to security reasons I keep my edit machine air gapped so there is no internet access. But I still need a machine for email etc. So I decided to attach an old pc monitor to my iMac as a 2nd display. That works great! So I have the iMac in target display mode attached to another mac and then a 2nd monitor attached to the iMac showing my email on the iMac. Weird back and forth I know, but the displays work. The keyboard however does not. Once I enter target display mode the only keyboard key that works on the iMac is "a" none of the other keys work. The mouse works totally fine, and this whole setup would function exactly how I want it to if I can get the keyboard to work.

So my question is does anyone know a way to have the keyboard work while the iMac is in target display mode?