External hard drive...maybe...but you know if you don't get this stuff off this drive you run the risk of losing it all. Burn it all to disks and get it off there. A hard drive only has so much space and then...if it is stuff you really want to keep then get it off the hard drive. You will lose it, without a doubt.
Here is your clue.....
now it's being very weird and a lot of things seem be be going wrong
If this were your car doing this would you even consider driving it across country? No you wouldn't. Time is short if a lot of things seem to be going wrong. You may not have much chance to save this stuff if you don't get busy now. If it crashes, and it sounds to me like this is what it wants to do, then chances are very good that all will be lost.