I try to install it through Galaxy 2.0 and it gets to 49% ... and then it just stops. Galaxy says, the game is downloading, but it never goes beyond the 49%.

Try downloading the standalone installer and using that. If successful, Galaxy should still find the installed game automatically, and it will end up the same as if you install via the client.

Tried that. It didn't work. Galaxy can't find the game.

But did the installation at least finish when you used the installer? If so, does the game run? I.E.: is it playable if you launch it from the desktop icon (or the executable in the installation folder)?

Either way, you should probably contact Support about this (though I gather they're terribly understaffed for dealing with the number of tickets they're getting these days, so be prepared to potentially wait for weeks for a real reply), but that would still be a way to play the game, even if the Galaxy integration isn't working.

Yes, I can play the game if I do a manual instal. I'll contact support.

Well, that's something, at least.
Good luck with Support Roulette! ;P