WS2812b led strip and arduino, should I give up?

Using Arduino LEDs and Multiplexing
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do you think that something like this:
Adafruit USB Isolator - 100mA Isolated Low/Full Speed USB : ID 2107 : $34.95 : Adafruit Industries, Unique & fun DIY electronics and kits

should help preventing this problem and making my computer "more safe"?

No I imagine the problem will still be there because their is no indication that their is anything to do with the USB connection.

Just power the Arduino separately and try the test again.

I quite agree with Paul__B in what he says.