Motor barely turns over and ground wire starts smoking and melts wire coating. already moved ground to different areas and this does not help.
Your starter (all starters) has a dead short at zero RPM, though it’s protected somewhat by ballast. As it rotates it generates a back EMF (voltage) that opposes the battery voltage. Since your starter is bogged down it is drawing too much current. That’s why it’s overheating the circuitry. Why it’s bogging isn’t clear from your description. But if you could describe the cause, you wouldn’t be asking.