To check some phrases

Could anyone please tell me whether the following VERY SHORT phrases are correct:

1) we set these yields equal to 1/2 of the error value

2) the model allows describing the process.

3) Do I need a comma before 'but' here: We have estimated the frequence not only for the strains, but also for the XXX strains...

4) Therefore, to describe the error frequence in them, we need to bla-bla-bla.
I think it's better to say 'in order to describe'

5) we need to put x=0 because the response will be zero.
I think 'to set' is better instead of 'to put'

6) it could be interpreted as the resulting probability of the error. 'resulting probability' sounds bad, imho

7) That is the main reason why...
Is it better to say 'this is the main reason why' or 'that is why'?

8) We have these and these results, just like in the experiment.
Do I need a comma preceeding 'just like'

9) Besides our previous studies, only a few research works are concerned with introducing the same characteristics of bla-bla-bla.
I think it's better to say 'Apart from our previous studies,'