Need advice getting these cooked-on screws out so I can replace my RTD (Oakford 790)

I’m trying to replace the RTD on my Oakford 790 and ran into a pretty big issue. The original sensor went bad and since NexGrill and every aftermarket place is still out of stock, I ended up ordering a Pit Boss RTD from Amazon. From everything I’ve read, these are pretty universal as long as the connector matches the control board, so I’m hoping it’ll work.

The part failing wouldn’t even bother me if I could actually find a replacement. I’ve had this grill for less than 2 years, and I’ve been calling NexGrill for months now — still backordered. They pointed me to two other companies and both of them are out too. So Amazon was my last shot.

Now the bigger problem: the screws holding the RTD in are completely destroyed. They’re rusted, rounded, heat-soaked, and basically fused in place. There’s barely anything left to grab onto. I’ve started spraying them with Seafoam Deep Creep to see if that helps at all.

I attached pics so you can see what I’m dealing with. If anyone’s had to deal with screws this bad on a pellet grill, let me know what worked for you.