Chronic Pancreatitis: Given the history of alcohol consumption (4 shots of liquor per week) and the sudden onset of constant moderate epigastric pain, chronic pancreatitis is a strong consideration. The patient's history of quitting smoking a year ago and the absence of other clear causes for the pain (e.g., negative lipase, no recent gallstone disease given the cholecystectomy) also point towards this diagnosis.

Gastroesophageal Reflux Disease (GERD): Although the patient does not report aggravating or alleviating factors, GERD can cause constant epigastric pain and is common in the population. The absence of a clear alternative diagnosis keeps GERD in consideration.
Peptic Ulcer Disease: Despite a negative H. pylori breath test, peptic ulcer disease cannot be entirely ruled out without further investigation (e.g., endoscopy). The patient's history of alcohol use and smoking could contribute to ulcer formation.
Non-ulcer Dyspepsia: This is a diagnosis of exclusion but remains a possibility given the chronic nature of the pain and the lack of clear evidence pointing to another diagnosis.

Pancreatic Cancer: Although less likely given the absence of significant weight loss, jaundice, or a more pronounced elevation in liver enzymes, pancreatic cancer is a diagnosis that must be considered due to its severity and the patient's age. The mildly elevated creatinine could be indicative of a mass effect or dehydration.
Mesenteric Ischemia: This condition can present with chronic or acute abdominal pain and is a critical diagnosis not to miss due to its high mortality rate. The patient's history of smoking increases the risk of vascular disease.
AAA (Abdominal Aortic Aneurysm): Although the patient does not have back pain or a palpable abdominal mass, an AAA could cause epigastric pain if it is large enough to impinge on surrounding structures. The history of smoking is a significant risk factor.

Zollinger-Ellison Syndrome: A rare cause of peptic ulcers and chronic abdominal pain due to excessive gastrin production. It's less likely but should be considered if other diagnoses are ruled out.
Eosinophilic Gastroenteritis: A rare condition characterized by eosinophilic infiltration of the gastrointestinal tract, which can cause chronic abdominal pain among other symptoms. It's a diagnosis of exclusion and would require specific testing for confirmation.