External hard drive nightmare

Hi all, first time posting but this site has helped me several times in the past so thank you for that,

Having an absolute nightmare with an external drive. I've got a Hitachi Touro Pro 4TB USB 3.0 that recently had some trouble with the power supply, over the last couple days the hard drive wouldn't power on if the power cable was hanging the wrong way off of the plug (if that makes sense), haven't had time to get a new power supply so have been dealing with it the last couple of days until I can get a new one.

Suddenly my hard drive stopped showing up in Finder, I checked Disk Utility and it's still there. The actual hard drive model and, stemming down from it, "EYES DRIVE" (which is what I named the drive) are both still there, but the EYES DRIVE is greyed out. I've tried verify disk which lead to a warning saying it needed repairing, but when I try to repair it I'm told the disk cannot be repaired and to backup any files and restore the drive. It also won't let me mount from that menu.

I've tried booting up to the Disk Utility menu and repairing from there to no avail, also tried DiskWarrior which tells me there's a hardware issue with the drive, I get the error "Directory cannot be rebuilt due to disk hardware failure (-36 2738)". I'm currently doing a surface scan on it with TechTool Pro, but it's a 4TB drive and this is proving to be taking a very long time. No bad blocks encountered so far but I'm only 15,000,000 blocks into a 976,000,000 block hard drive.

What are my options here? The data on the drive is extremely valuable and I cannot really afford to lose it. Is it a good sign that the drive name still shows up in Disk Utility or am I still in big trouble?

Also, I realise I should have multiple backups of all of my stuff, but this drive originally started off as a backup drive that I would keep safe and not touch except for backups, until I got a new retina MacBook Pro and the lack of space on it (256GB) forced me to use it as storage as well as Time Machine backups. There's about 5 years of hard work on it, I'm absolutely kicking myself that I didn't have it backed up elsewhere.

Thank you for any responses and let me know if you need any more info, I'm really freaking out here!