I had a similar problem with coverage in my house, my phone line and router were in the office and I couldn't get wifi to cover the whole house from there, especially not in the upstairs bedrooms where streaming any kind of video was impossible.
I also used homeplug plug in WAP's temporarily which improved things but I found them a bit temperamental with my old wiring and I have a suspicion they affected my DSL line. In the end I bit the bullet, drilled holes and ran an ethernet around the outside of the perimeter of the house and back into the living room where I sited a switch and a second WAP, this also allowed me to have wired ethernet for my media devices (TV and Media server) which solved all the 4k video streaming issues etc. My ultimate plan was also to put a third WAP unit upstairs but this proved unnecessary as the two WAP's provided plenty of coverage.
I have 2 Unifi AC Pro's, it looks like they can be had for £50 pre-owned on ebay. I don't run the controller software, the WAP's have been completely reliable - really good.
I haven't had much luck with home networking consumer stuff generally from Asus, Netgear and TP-Link, I particularly avoid TP-Link stuff as I have tried their devices in the past and they pump out models so fast that they stop firmware updates after only 1-2 years and I have frequently had reliability issues with their equipment, I do have some Netgear Prosafe network stuff. I generally try and steer clear of the weird gamer stuff, routers that look like spaceships
Maybe you should take a deep breath and get your hammer drill out ? Anyway I hope you get it sorted shortly.
C
