What ISP Service do you have? Cable or DSL?
What ISP Modem do you have? Stand Alone or built in router?
What ISP Modem brand and model do you have?
If this modem has a built in router, it's best to bridge the modem. Having 2 routers on the same line can cause connection problems.
Ensure DNS IP addresses are being filled in under Setup/Internet/Manual?
Turn off QoS options. However you may need to enable this for the PS and your PC while he's gaming so that when he's online and gaming, you and the PC can still get Internet.
Turn off Advanced DNS Services if you have this option under Setup/Internet/Manual.
Turn on DNS Relay under Setup/Networking.
Setup DHCP reserved IP addresses for all devices on the router.
Ensure devices are set to auto obtain an IP address.
Set Firewall settings to Endpoint Independent for TCP and UDP.
Try mixed G and N?
What security mode are you using? WEP, WPA or WPA2? Preferred is WPA-Personal. WPA2/Auto TPIK and AES.
Disable Short GI and Extra WiFi Protection.
I would turn off Protected WiFi and Wish.
Maybe someone can review your router settings with you using
Teamviewer.com.