Final answer:
The correct sentence is 'I should have run to the mall, but I got really tired and would have had to sit down by the fountain for a break.'
Step-by-step explanation:
The correct sentence that fixes the error in the question is: C: I should have run to the mall, but I got really tired and would have had to sit down by the fountain for a break.
The phrase 'should have ran' is incorrect because the past participle of 'run' is 'run,' not 'ran.' Therefore, it should be 'should have run.' The phrase 'would had have to sit' is also incorrect; the correct form is 'would have had to sit.' The corrected sentence maintains past tense coherence throughout.