@Forbesisle
1. Normally after you finish the WPS process, the WPS LED will be off, so it will not stay on all the time
2. If the PC still receives good signal from your router, you could still connect to router WiFi, however, in other areas where router signal is too weak to use, you could try connecting to the extender WiFi
3. Regarding the speed difference, please note that the extender needs to transfer the Wi-Fi signal from the main router and also communicate with wireless client device, and transformation would make the speed slower, so it is normal that the extender speed is not as fast as the main router.
The extender is to kill the dead-end of your house, so the signal strength in the area where there was no router signal will be improved. But since it needs to get the receiving signal from the main router, the speed depends on the quality of the receiving signal.