Heart Failure (HF): Given the patient's history of CAD, hypertension, and symptoms of shortness of breath (SOB) with activity, swelling of legs (edema), and weakness, heart failure is the most likely diagnosis. The presence of a systolic murmur, diminished lung sounds, bilateral crackles, and 2+ edema of the lower legs further supports this diagnosis.

Chronic Obstructive Pulmonary Disease (COPD) Exacerbation: Although less likely than HF, COPD exacerbation could explain the SOB and diminished lung sounds, especially if the patient has a history of smoking or COPD.
Pulmonary Embolism (PE): While less likely, PE should be considered given the acute onset of SOB and the presence of leg swelling, which could indicate deep vein thrombosis (DVT).
Anemia: The patient's weakness and SOB could be attributed to anemia, especially if there's an underlying cause such as gastrointestinal bleeding or nutritional deficiency.

Acute Coronary Syndrome (ACS): Given the patient's history of CAD and stent placement, ACS (including myocardial infarction) must be considered, as it can present with similar symptoms and would require immediate intervention.
Cardiac Tamponade: Although less common, cardiac tamponade can cause SOB, weakness, and hypotension (the patient's BP is 110/54), and is a life-threatening condition that requires prompt diagnosis and treatment.
Pneumonia: Community-acquired pneumonia could explain the SOB, diminished lung sounds, and bilateral crackles, and would require antibiotic treatment.

Constrictive Pericarditis: This condition can mimic heart failure but is less common; it would require specific diagnostic tests like echocardiography or cardiac MRI to confirm.
Cardiac Sarcoidosis: A rare condition that can cause heart failure symptoms, but would require further testing such as cardiac MRI or biopsy to diagnose.
Amyloidosis: A rare condition that can cause heart failure, but would require specific diagnostic tests like biopsy to confirm.