Divalproex sodium has affected my platlets and red blood cell indices (e.G., mcv). Does Neurontin (gabapentin) have similar effects?

No . Neurontin (gabapentin) has a more favorable side effect provide as compared to valproic acid. Hematologic derangement is extremely rare with neurontin (gabapentin). Valproic acid may however be more effective in the treatment of your specific epileptic disorder.
Neurontin (gabapentin) likely . Won't cause above blood picture. Leukemia and the chemotherapy would likely contribute to the low cell counts more than the meds you mentioned. http://en.m.wikipedia.org/wiki/neurontin.