There is not an expedited line for shorter layovers but if you do think you will miss the flight because of slow processing you can talk to a CBP officer working the lines about missing your connection. They MAY move you forward but also may not.

Is this all on 1 ticket? If so DL will rebook you on the next available flight to LAS. If not, you should reschedule your second flight to a later time as you do not have a connection that will be protected. I think the MCT (Minimum Connection Time) at DTW is 80 minutes but maybe that has been reduced recently allowing for your 75 minute ticketing.

You are correct that you will clear passport control, get your bag(s) and then deposit them at bag drop if on 1 ticket.