there is a very different atmosphere in the town this morning than there was yesterday.
ambiguity of place i.e. the town's morning atmosphere was different than which place of yesterday atmosphere.'There' is less formal and it is forbidden in formal writings.
so my suggestion is,sentence should be
The morning atmosphere of the town was very different than it was on yesterday.
incorrect:Neither Farooq nor Akbar are going to the wedding lunch on Saturday.
Here the subject is neither which takes singular form so very easy to correct
Neither Farooq nor Akbar is going to the wedding lunch on Saturday.

incorrect:
I will not be surprised if he doesn’t turn up tomorrow.
future action with respect to future follows simple present tense for time tables of trains, hotels,and tv shows.Here we are talking about a person so it is incorrect also there is some sense of certainty not 100% surity, so sentence must be
I would not be surprised if he doesn’t turn up tomorrow.
or
if he doesn't turn up tomorrow, i wouldn't be surprised.
remember contractions are less formal in writings. so contractions could also be corrected.
incorrect:Every one must decide themselves what to do about it.
every one is singular reflexive pronoun and singular verb.A kind of subject
verb agreement.also identifying clause is there,so no need to put the coma in the middle of the sentence.
correct sentence:Every one must decides onself what to do about it.

incorrect:
I compared his essay with Mushtaq’s and found them to be almost identical.
correct:When i compared his essay with that of Mushtaq,i found both of them identical.