Yes.

Correct for the most part. You can still have very high relative humidity with a low WBT if the dry-bulb temperature is also low.

When the WBT gets above 35°C, it’s not only dangerous, but positively lethal when sustained for even the healthiest person as sweating (or any other form of evaporative cooling for that matter) can no longer keep the body at a suitable temperature.

I’ve seen the term misused a lot recently, so I’ll state that a wet-bulb is a part of a measurement instrument. Wet-bulb temperature is a measured quantity (along with dry-bulb temperature, pressure etc.) and an Extreme wet-bulb temperature event is what actually kills people.