I've told you several times now, QR has rates about $2700 between IAH and IST, here is an example:
https://flights.app.goo.gl/B1oo5

Why would you fly AA or BA in business, when QR is vastly superior, and less expensive? Yea, you'd have to get yourself to IAH, but I'm certain you can figure that out. It is a bit more for the QR flight from DFW and requires an overnight at DOH.