1. As mentioned in the dialogue, 场 is used as a measure word for events. You could also use it to describe 一场雨, 两场棒球赛, 三场宴会 etc.

2. 把我吓死了 could be thought of as a more extreme version of 我被他吓到了.

3. 出 is used to describe “having” an accident as in 如果出车祸的时候有人受伤了.

4. 闯红灯 is equivalent to “running a red light” in English as seen in 他看到一台摩托车闯红灯.

5. 停下来 can be thought of as meaning “to come to a stop” as seen in 所以应该是他来不及停下来才撞到别人的车子吧 and 没办法马上把车停下来.