@JumpingMonkey 

Do you happen to have another PC to wire or use a different device to test the speeds? Mainly to see if the issue is happening across all devices or just this PC.

Another setting you could look at in the router is located in the NAT menu. Make sure "Current Hardware NAT Status" is not disabled. If it is already enabled, disable it, save then enable it again and test.

I don't have another PC to test, but my PS4 is reporting ~90Mbit.  

Plugged straight into the ISP modem it's normal ~200Mbit.  

I tried looking, but I can't seem to find NAT settings on my router. I searched my issue and people were saying to disable some NAT settings, but I can't for the life of me find ANY NAT setting in this router. 

Also, if this helps, my PS4 is reporting NAT as "Type 2"

@JumpingMonkey 

Your router is a v1, the NAT boost seems to be only on the v3.

You could try opening ports to see if that may help with the speeds. Type 2 is the gaming system saying not all ports it uses are opened for communication.

Go to virtual servers, add a new entry, enter the port the gaming system uses. The IP address is the IP of the gaming system, protocol leave on "All", and do not touch the common service port.

Here are the ports the PS4 uses:

Port 80 (TCP), Port 443 (TCP), Port 1935 (TCP), Port 3478-3480 (TCP), Port 3478-3479 (UDP)