I have little to offer except for an opinion. If your engine compartment has a fire, get away from the car and let it burn until proper equipment and personnel arrive on the scene. That 2.5lb bottle? Use it for egress or to buy time for egress if you are ...delayed. The cost of the car is nothing compared to the cost of having your body burned.
Fire happens fast in cars. Here's an article from GRM:
https://grassrootsmotorsports.com/articles/how-i-became-human-torch-and-survived/
Here's a video:
Escy posted some info on his build on this forum, but most of it is detailed
elsewhere. Here's his video of the car burning.