Hi could you get access to Internet when you connect only one connection? For the ip respecting, I was wondering if you're mentioning ping test of packets via ICMP. It's may be about Online Detection...

;)Really weird demands. I don't think any mechanism could reach it. Why not establish PPTP client to lan directly with the "remote router"? ps. you could upgrade into V3 firmware.

So to exclude influence of DNS, could you ping your server' s IP address successfully when IPsec client to lan is established?

TL-ER6120 v2 is a high end product for tplink and it's a nice choice. But you want cheaper, I suggest TL-R600VPN V4.

You're right for the account name. The old hardware version of smb router indeed cannot set as more than one 0.0.0.0. But not for their latest version, like TL-ER6120 v2, TL-R600VPN v4, and so on.

The screenshots are vague and I think you'd better contact tplink support.