Function comes before fashion. So this is a common issue one never hears about? I find that interesting, if not unlikely. Maybe the manufacturer/retailer isn't the entity to give you advice? Maybe someone in construction has a solution? Maybe a flat metal surround would be in your aesthetic?

You have a nice bump out for something spectacular. Please take pics so that the entire room can be seen.

I have never heard of this issue get an actul inspector out to check this FP install and function

Is that plaster or drywall? i have the almost identical in plaster & never had an issue with splitting. I‘ve seen some really nice porceline fireplace surrounds that look good.

The framing of the fire has little to do with a "to code" fire surround within that framing, and then receiving drywall or any other finish material

Your info source is full of c.r.a.p.

Who built it into the wall and installed the box? Start there. If your tv , (installed at normal code/ about 50 odd inches above floor) were above that fire ? You might be on your third tv by now: )

Add a modern mantel. You need the heat diverted up and AWAY from the wall....tv or no tv

A clean and simple white oak, as your built in under the tv. May be all that is needed to disperse the rising heat.

The drywall needs to be replaced with a single piece around the fireplace. Any seams around it will probably crack.