DHCP assigns wrong IP address on the wrong domain. Probably a wrong setting somewhere on my MAC.

The IP address you are seeing on IP2 is what is known as a "self-assigned" address. That means that when your Mac is connecting this network, it is not getting the proper IP address from the network's DHCP service.

My guess, at this point, is the configuration of the DLink extender.

Let's start with what is the make and model of your "main" wireless router? Is the DLink powerline adapter connected on the same electrical circuit as your main router? That is, if you "pull the circuit breaker" at the electrical panel, do both devices not get power? Finally, do you have any proxy server settings configured for your Mac, i.e., System Preferences > Network > Wi-Fi > Advanced... > Proxies?

169.254.xxx.yyy is a self-assigned IP address.

This sort of address is assigned by your Mac to Itself when it starts up. It is needed to identify itself uniquely on the Network.

I most cases, with a properly operating Network, this address would be sent out once in a broadcast message, for all listening, that says essentially "send a good local IP address, back at this temporary self-assigned IP address". That is usually the last time that address is seen, as the response from a Router comes back so quickly, most Users have never seen a self-assigned IP address.

So when you see a self-assigned IP address persist, it tells you, "nobody will talk to me". In most cases, this is caused by really fundamental problems, like cables unplugged.

Remember that packets going toward the Internet are sent to the Interface that is BOTH TopMost AND Working shown is System Preferences > Network.

If you stall have Wi-Fi active, it is possible you have not generated any traffic on a port that is not Topmost and Working, so it has not yet sought a good local IP address.

That proxy information is correct, and that is NOT the solution to your problem.

RE: power

Are you in the US (which typically uses 120 Volt two-phase power) or somewhere else like the UK (which typically uses 240 Volt one-phase power) ?? Does your main breaker break two wires or one?

With two-phase power, you could be on a circuit on the opposite Phase from the Router. This would mean the place where they connect is at the neighborhood transformer, and that could add some rather long wires.