If I am in section 8 and I lose my job, would the amount I pay for rent, be decreased, till I find another job?

you have a 'lease' with the Sec 8 and like any lease it cannot be changed during the course of it
if you lose your job and cannot pay the rent, you most likely will be evicted

No, it is not reduced. You will be evicted if you do not pay your rent due. Without a job, you won 't qualify to stay there either so, keep paying the rent. As soon as you stop and they realize you no longer have a job, expect to be evicted.

Have you read your lease? Would you be allowed to remain in the apartment?

No it would not. It would not change at all. You owe the rent in the lease, period.

If you are in section 8 you should have been informed of the rules. If you have a social worker you could ask them.