Two galaxies aligned in a way where their gravity acts as a compound lens

One fun thing think about is that these two galaxies are only aligned from our perspective in the universe. Viewed from a different location, and they're just two normal galaxies.

Also, imagine having the technology to send signals through the lens and get the attention of intelligent life on the other side.

I’m sure there are plenty of civilizations that have done this, but on the time scale of the universe no one happens to look at just the right moment.

But wouldn't the size and age of the universe also imply that someone has looked at just the right moment somewhere somewhen.

Don’t radio waves weaken proportionally to the square of the distance? No one would be able to detect them past a (relatively) small distance.

The energy density drops off as inverse square law, but the photons go forever. Radio is just photons (light) so it goes forever until it interacts with something it hits. The expanding universe will stretch it's wavelength slightly however.

Regular EM Radio waves are not photons. Photons have special configuration which prevents leaks into surrounding space, while regular radio waves are just waves.

Nope. Radio waves are made of photons. All EM waves are made of photons.

Photons are EM-waves. Are photons made of photons?

Great, now add to that the fact that radio waves are an EM-wave too, and that answers your original confusion.