I disagree with your immunity claim. In order for a chief executive to operate while chief executive they require immunity. Because there is process where he can be charged, convicted and removed doesn't change the fact the chief executive has immunity. Otherwise he could be charged and convicted in any state or county or municipal court in the country and tied up from performing his duties. It would be the easiest method for the opposition party to make them impotent.
My feeling, theory, or understanding, or whatever you want to call it is that The President of the United States is that the founders set up the chief executive of the United State just like a King except for the impeachment, conviction, and removal clauses and other limitations in the US Constitution. Just like congressman and senators have immunity when going to the Capitol to vote (Their single most important job as elected by the people and the states) and cannot be arrested or even detained at that time the president of the United States has immunity, limited in some explicit cases, from prosecution. Why, because the duly elected chief executive elected by the people would not be able to lead effectively without a broad immunity save checks and balances.
I am not saying he does not have immunity the Constitution says it. Suggest you read Section 4 of Article 2 of the Constitution. If the President commits high crimes and misdemeanors, the remedy is impeachment therefore he is not immune to prosecution while in office. Trump was impeached over J6, the impeachment trial ended without his removal from office. He was charged, tried and not removed, my question is would trying him again 3 years later constitute double jeopardy. Would it even be legal to wait for him to leave office before charging him. I guess SCOTUS will decide that. But as far as my claim he does not have total immunity the Constitution agrees with me.