Ext HDD is being recognized, but primary partition isn't

I've been using this ext hdd for years and recently have been more and more trouble with it. I've looked all over google and many different forums for a possible solution, I've found many similar questions to what I'm looking for, but unfortunately my problem is slightly more complicated. I'd really appreciate any help or advice I can get, as I'd really rather not lose the data on the drive, and with my specific problem, I don't even know if reformatting it will actually solve anything.
First off the drive has been split into many different partitions that most likely aren't configured properly. At one point the only computer I had didn't have a hard drive in it and I was only able to use it with live OSs loaded on flashdrives, so I figured to make things easier I would set up the ext hdd with multiple Linux OSs and start using the ext hdd as an internal hdd. I'd never done anything like that before, and I had only learned how to load a live OS onto a flashdrive a few months earlier, I had some difficulties with loading more than one OS and reconfiguring the grub, and basically just bagged the whole idea as it wasn't that important, just would've been more convenient. So since then my ext hdd drive (1tb) has been set up with one 850gb primary partition that I use for storage, a 5gb grub partition, another even smaller partition that was suggested in the instructions I was following on how to load the multiple OSs and I can't remember what it was called, it wasn't for loading an OS onto, but something more along the lines of a grub or recovery partition, and finally five different 20gb partitions that I was going to load up with OSs before I gave up on that idea. Since then the drive has always worked fine, both Linux and Windows recognize all 8 partitions and I've always been able to access any data in either OS. After a while everytime I plugged it in I would be getting errors on different partitions, saying they needed to be scanned and fixed, and later just saying they needed to be formatted before they could be used at all, but never had any problems with the main 850gb partition, which was the only partition I was worried about as it's the only one I use.
Secondly, the usb cord that connects the ext hdd to the computer has been getting worn out this last year, and the last few months it has become increasingly more difficult to get it to work. The drive always lights up when plugged in, so the power isn't a problem, but I have to flip the drive over sometimes, twist the cord awkwardly, and sometimes just continually unplug and replug it before the disk will start spinning, many times the light flashes for a minute as if it's trying to connect, but if you feel the drive case you can tell that the drive isn't even spinning, and obviously the computer doesn't recognize it at all when it does this. Usually once I get it to connect it works fine until I'm done with it and unplug it (unless I accidently bump the drive or cord, then it immediately disconnects). Recently it's been a lot slower at recognizing all the different partitions, the 850gb partition I use was always the last one to be recognized, but it would always show up eventually and work. Lately the drive in general has also become a lot slower, sometimes transferring files take around 200x longer than they should, so larger files like movies I just have to cancel the transfer and figure something else out. Loading and displaying all the files that are already on the drive have been taking much longer as well.
So today I plugged the drive in, same problems as usual occur, however the 850gb partition I use is no longer showing up no matter what I try with the drive. After messing with disk manager I can see that the partition is technically still there, however now it's only labeled as "G Drive" and needs to be formatted before it can be used. In disk manager that partition is actually labeled as healthy and working properly with an up to date driver, but when I try to open the drive or scan for errors it tells me the computer can't access that drive and that it's offline.
I've run out of ideas as far as trying to fix the thing through Windows. Next, I'm going to load up a live Linux OS and see if that makes any difference to the drive, I've also got a different laptop I'm going to try connecting it to, however that's the computer I mentioned above that has no internal hdd, so I can only run a live Linux OS on that one. Hopefully Linux will recognize it properly, but I would really like to fix that partition somehow to get it recognized in Windows again, otherwise transferring and backing up the data currently on the ext hdd is going to be much more difficult for me, not to mention time consuming (the 1tb ext hdd is about 4 times larger than any of the other hard drives I have access to, so I could only transfer at most 1/3 of the data on the ext hdd at once, and all my other hard drives are already pretty full).
So there it is... If anyone knows how to fix this problem, I would very much appreciate some help, even if you don't know for sure, any advice is welcome. I'm aware that the deteriorating cord may be to blame, and simply buying a new cord would be an obvious solution, but the drive itself is over 5 years old now, and I don't know how to determine if the drive simply needs a new cord or if the drive itself is on its last leg. If the drive itself is about to die I don't want to waste my time and money buying a new cord...
So again, any advice at all would be greatly appreciated.