What will be the tipping point
We live in a nation of laws, and although - for whatever reasons - the people elected a lawless executive, it is almost unthinkable that the military would intervene in civil government. That is for 3rd world countries.
In his first term he was clueless and ignorant, but this time not only is he more experienced but he has help (the "nerd reich") behind him.
The 25th Amendment specifies that it is up to the VP and either the cabinet or one house of Congress to start the proceedings, and while that is almost certain to happen after the midterms, it is not likely to happen before.
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25th Amendment - Section 4.
Whenever the Vice President and a majority of either the principal officers of the executive departments or of such other body as Congress may by law provide, transmit to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office, the Vice President shall immediately assume the powers and duties of the office as Acting President."