[alright1234 (OP)]

How much fuel was used to decelerate the Apollo 11 CMSL at the moon?

[Petrochemicals]

I dont know, but for a rough idea for you to calculate it you would need

1)The orbital velocity appolo 11 around the  moon
2)The mass of the landing capsule
3)the height of the moon orbit

The energy contained in the spacecraft velocity.
The energy difference is potential in orbit minus the surface.

Given that all frictional losses are negligable on earth, you know therefore how much energy had to be counteracted. There is no terminal velocity, so very very easy.

Then there is the energy used in simply hovering, this will be the time taken to go from orbit to touchdown at the energy of  average  gravitational midpoint, by the mass of the spacecraft.