These symptoms, chest heaviness, pain, sweating, and nausea, can sometimes mimic indigestion but are classic warning signs of a heart issue, especially since the antacid did not help. Please do not give any more self-medication. Seek emergency medical care immediately or take him to the nearest hospital. While waiting for medical help, you can have him chew a single tablet of uncoated aspirin (325mg) if he is not allergic to it and has no bleeding risks. Keep him calm, sitting comfortably, and resting. Please act quickly to ensure his safety; a professional evaluation is critical right now.