If you get dropped it will be because of the accelerations out of the corners, especially the 180. The closer to the front you are, the smaller they will be. At the back of a pack that size, you’ll be bouncing between 30 and 50 km/h 5 times a lap. Cornering well and maintaining momentum will determine your fate.
As for crashes, races like you describe (field and course) tend to get strung out pretty quick which is safer than a big bunch. You’re pain will be endless 600 watt digs out of the corners, not road rash 
ADD: if you do get gapped, stay in as long as they let you and work on your cornering. An open crit course is a rare opportunity.