Normally a WiFi router will broadcast at about -20dbm. The signal falls off with the square of the distance so the further from the router the weaker the signal. -27dbm is a very strong signal but your WiFi adapter should handle it without a problem. The fact that a speedtest shows the expected 100MB is a good indication that you don't have a problem with the WiFi. You can verify with a ping test:
On a Windows PC:
right click on Command Prompt and Run As Administrator.
ping -n 100 22.214.171.124
Hit Enter. Wait until it finishes. Will take a minute or two then it should say:
Ping statistics for 126.96.36.199:
Packets: Sent = 100, Received = 100, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 20ms, Maximum = 32ms, Average = 23ms
If your WiFi is good you should see Lost = 0 on the second line. (Numbers on bottom line may vary)
Slow loading Webpages can be caused by too many ads on the page (Get the Ublock Origin extension for your browser, F B Purity extension if Facebook is the problem), too many browser extensions (Go in to Settings on your browser and disable all extensions then restart the browser), Busy CPU ( search for Task Manager and hit Enter then click on More Details. CPU usage over 50% can cause the browser to be slow), Busy or slow Hard drive(an SSD will make a big difference in how fast a browser loads. In Task Manager check Disk Usage (should be very low), Low Memory (In Task Manager check Memory usage. If 50-80 is OK. More can cause Page faults where the PC has to store data on the hard drive instead of the RAM and that is much slower.). Try Speedyfox. http://www.crystalidea.com/speedyfoxIt can speed up Firefox or Chrome things a bit.