slower speeds SXS80

The house is nearly 90 feet long but only 20 feet wide and on 3 floors. It is a very interestingly designed house with fairly thick walls and a lot of iron framing. This is an older house built by a wealthy family and I'm not entirely certain as to what was happening in their minds when it was built. Because of the way the Internet comes in the house I'm forced to have the SXR80 in the basement.The basement for practical purposes is like a bank vault.I'm not sure why it was constructed the way it was constructed. Right above the spot where the SXR sits you barely get the Wi-Fi signal on the 1st floor and on the 2nd floor is non-existent.once you move 30 feet in either direction from that vertical position even on the 1st floor there is no signal.  I started out with 2 satellites and try to place them pretty strategically.However there were some spots with half the signal strength  On the outer zones of the highest floor. So I bought a couple more. This was done with an understanding that as long as there is backhaul ethernet it will not slow down the overall speeds.Perhaps the was wrong information?having said that the speeds are no better when I only use 2 or 3 satellites.when I disconnect all satellites and stand 10 feet away from the router the speeds go up to 650 up/750down or so..thanks

Thanks for taking an interest in this. Here is what the network looks like. I disabled all other SSIDs but the main one and vlan was disabled. I m checking speeds with speedtest app on my Google Pixel cell phone with adaptive connectivity switched off standing about 5-10 feet away from a SXS 80.