Nozzle jiggles when screwing into heating block
If the threads are damaged badly enough not to hold a nozzle rigidly, you should replace the heating block, but there might be hacks you could do to keep using it for a while until you're ready to replace. I've had luck replacing threads in completely unrelated applications with epoxy, and if you can get one that handles and transmits the heat well enough (maybe JB Weld? not sure) it might work here.

I don't think there's any indication you need to change to a different kind of heating block. That would only be indicated if there were lots of other people reporting the same problem you're having with your printer model or similar ones. It seems more likely that, if they're damaged, you just did it by over-tightening or over-vigorous cleaning with the brush.