Nighthawk AX8 (RAX80) Coverage?

Hi,

Yesterday I upgraded my wi-fi router from Netgear AC1600 to Nighthawk AX8. The installation went well with no hickups and latest firmware version was installed. 

My concern is the coverage area of the AX8 is no better at all then that from my older AC1600. I read a lot of reviews regarding the coverage area and the consensus was positive.

Before yesterday in order to get a signal to my back bedroom to my TV I was utilizing Netgear AC1200 Extender. To get a signal in the same room with Nighthawk AX8 I had to install the Extender again. This was not what I was expection at all!

The distance from where the router is installed to the bedroom TV is approximately 35'. What am I misissing here? One of the "wings" is pointed in the direction to the bedroom, if that makes a difference. Also, if it makes any difference at all, the router is in the family room that has 3 exterior brick walls. But the router is butted next to an interior sheetrock wall.  

I have attached my house layout. It is single story ranch.

Any advise would be greatly appreciated.