I bought two new disks to use instead of the broken drives.
As one of the broken drives had matching PCB and chip numbers as the non-broken one, I attempted a swap. But it just resulted in the drive beeping and clicking, same thing happens when I move the PCB back to the previously working disk. Luckily I had made an image of that disk in advance. I am now in contact with some data recovery companies to get a quote for the cost :(.
Apparently the pre-amp of the heads is fried too, and putting the PCB on the disk with a fried pre-amp fries the PCB. Ugh, this will need open disk surgery and a cleanroom to fix, not going to be cheap.
That’s a shame. I hoped you could avoid the expensive clean room recovery.
It is a reputable company and one of the earliest and best known companies for consumer level, cheap online backups. There are others now but mozy is just as safe as any other encrypted transfer (which was one of your questions). It gets really good reviews and is not some fly-by-night company. I know for a fact that it works well and almost painlessly. You can try it for a much smaller number of files for free or even just keep it to that. There is literally a danger of your living space getting destroyed at all times. You need offsite storage to get around that and there are several ways to do it but online backups are probably the cheapest option for very large amounts of data.
You could also just buy your own website and domain and store stuff there. It doesn’t cost much at all these days and you get lots of storage that you can use to backup files if you choose to even if you don’t display them to anyone else. I have one and it is less than $10 a month when spread over the whole year. You get lots of other benefits as well like as many e-mail addresses as you want plus countless other things. You obviously get your own website and domain as well. The operating system shouldn’t matter for that but you may have to handpick the files and folders that you want to update and do it manually from time to time. It still doesn’t take very long.