how to see if a font is safe to download

Short of downloading it and trying it, there's nothing you can do other than to only download from a trusted fond foundry. There's no way to "pre-test" a font, nor to ensure that the file you download doesn't actually contain malware.

Regards.

You can never know if any download is safe, all things may and can go wrong.

Always have a current backup, then you can recover from something that goes wrong.

I have never heard of that, but I can't say that it is impossible.