Mesenteric Ischemia: Given the patient's age, history of type 2 diabetes, and the acute onset of abdominal pain after eating, mesenteric ischemia is a strong consideration. The pain is often out of proportion to the physical examination findings, which aligns with this patient's presentation of not being overly tender to palpation but having right lower quadrant tenderness.

Acute Cholecystitis: The right lower quadrant tenderness could suggest acute cholecystitis, especially if the patient has gallstones. The absence of nausea and vomiting does not rule out this diagnosis.
Diverticulitis: Although less common in the right lower quadrant, diverticulitis could present with similar symptoms, especially in an elderly patient.
Intestinal Obstruction: The patient's symptoms could be consistent with an intestinal obstruction, particularly if the "spoiled salad" led to an intestinal blockage or if there's another underlying cause for obstruction.

Appendicitis: Although the patient's age and lack of typical migratory pain might make appendicitis less likely, it is a diagnosis that cannot be missed due to its potential for severe complications if not promptly treated.
Aortic Dissection: The patient's hypertension and age put him at risk for an aortic dissection. Although the pain typically radiates to the back, the absence of this symptom does not entirely rule out the diagnosis.
Perforated Visculitis or Ulcer: Any condition leading to perforation of the gastrointestinal tract is an emergency and must be considered, despite the patient not showing signs of peritonitis.

Eosinophilic Gastroenteritis: If the patient consumed something in the salad that triggered an allergic response, eosinophilic gastroenteritis could be a rare but possible diagnosis.
Infectious Causes (e.g., Yersinia, Salmonella): While less likely given the absence of diarrhea, nausea, or vomiting, infectious causes cannot be entirely ruled out without further testing.

The workup for this patient should include:

Complete Blood Count (CBC) to look for signs of infection or inflammation
Basic Metabolic Panel (BMP) to assess for electrolyte imbalances and renal function
Liver Function Tests (LFTs) to evaluate for liver or biliary disease
Lipase and amylase to rule out pancreatitis
Imaging studies such as a CT scan of the abdomen with contrast to evaluate for mesenteric ischemia, intestinal obstruction, and other causes of abdominal pain
Consider an ultrasound if gallbladder disease is suspected
ECG to evaluate cardiac function, given the patient's age and hypertension, to rule out cardiac causes of abdominal pain (e.g., myocardial infarction presenting atypically)