Yeah, if you can get on KLM that's safer. Usually SLC is a small airport and 30 minutes is fine. Just little room for additional issues. LAX can have fog in the morning ("June Gloom") this time of year as the weather warms up over the cold Pacific. I was delayed 45 minutes from SFO-LAX due to ATC holds due to fog last week.

But technically it is a valid connection and your bags will transfer without issue if all is on-time. And yes, there is padding to all DL flights.