This seems a pathetic amount of compensation - although years ago, I got 10k avios for having to wait 45 minutes to be deplaned.
I would write a strong, matter-of-fact letter to CR stating that their current offer is totally unacceptable given the gravity of your complaint. You shouldn't need to do it, but push and shove! (Years ago BA insisted that one of their flights arrived 3:56 late so would only pay 300 compensation - insisting (correctly) it was over 4:00 I finally got the full 600 - but only until I was blue in the face!). Check websites like Which? which usually has some standard complaint letters/advice.