In remote end, you need two routers on each site. And on the router in india, you can add two IPsec VPN tunnels.

Which driver did you try to install? Describe the problem in details when installing the driver.

Firmware is up to date? Describe Wi-Fi connectivity issue in details. When connection drops, how about status of wireless network connection? Can you reconnect? Normally how do you make it connect...

It should be a compatibility issue. No solution here...:( You may buy a new USB dongle which in compatibility list of MR3040.

No worries if no problem with your internet connection at all. When the root DNS sever blocks ping, it will show Ping root DNS fail in Diagnostics. But it won't affect internet connection.

Does the cooling pad help to keep the router cool and internet speed won't be affected anymore? If it helps indeed, why not use it to cool my router all day?