A 3-year-old boy from rural Maharashtra presents with severe hypoglycemia (blood glucose 35 mg/dL), hepatomegaly, and lactic acidosis (pH 7.2, lactate 8 mmol/L) after a 6-hour fast. His parents report recurrent episodes of seizures triggered by fasting. Liver biopsy shows excessive glycogen accumulation with normal structure. Enzyme assay confirms glucose-6-phosphatase deficiency. What is the most appropriate immediate management?