Congress only gets involved AFTER it is invoked after/if the President contests it.

To invoke it requires the vice president and a majority of sitting Cabinet secretaries to decide that the president is “unable to discharge the powers and duties of his office,” they can simply put that down in writing and send it to two people — the speaker of the House and the Senate’s president pro tempore.

Then the vice president would immediately become “acting president,” and take over all the president’s powers, at least temporarily.

Thus one vice president and any eight Cabinet officers can, theoretically, decide to knock the president out of power at any time.

If the president wants to dispute this move, he can, but then it would be up to Congress to settle the matter with a vote. A two-thirds majority in both houses would be necessary to keep the vice president in charge. If that threshold isn’t reached, the president would regain his powers.

The latter is the hard part because invoking is only the start of the process and the latter needed to continue it. Of course given the presence of the sycophantic Pence and cabinet, none of it would be easy.

Is there any provision for acting cabinet members?

Pence would NEVER doom his "god-given" chances @ the oval office by doing this. He could just wait til say march when Trump resigns to avoid prison...

He's not going anywhere. Every day in every way he is making it clearer and clearer that he will never give up that office under any circumstance. He is not going to commit suicide for those who are wishing he would (and soon). He will never "lose" an election. It will always have been "rigged." I am convinced the only way this evil suppurating boil on the entire population of the planet's collective asses will ever be removed from his self-imposed dictatorship is feet first wrapped in a plastic sack.

...that he thinks he has to push Americans around. We need to show him how powerful he is by not giving in one iota. This is the only way to stop him.
Mr. Trump has no power. Let everyone know.

Guess what? Insane tactics often work - they have for Trump for 72 misbegotten years. It won him the Presidency, legitimately or not. He doesn't give a flying fuck how long the shutdown lasts. Neither do his voters as long as their checks keep coming.

It is not crazy. It is deliberate. He picked an opportune time, when the pain of the shutdown would be minimized (public inattention, federal workers taking vacation) and propaganda value maximized.

Don't buy his act.

That is the key sentence in you post. republicans can ignore all sorts of injustices as long as it doesn't affect them.

SSI, sure.

SNAP is resented by many (most?) working-class Trumpists - like Disability or TANF checks are. SNAP goes to the most impoverished in the country, and by and large, the poorest Americans don't vote.

I assume SSI will continue, as Trump is not insane.

Another possibility is that this is, in essence, a deliberate attack on the United States. I mean, think about all the things a foreign enemy might do to attack an enemy without actual military force. You'd destroy the infrastructure - in this case removing all environmental protections, all personnel to run the place. You'd create chaos. It's really a variation on the novels that have been written about attacking the power grid, for example. We'd be, literally, powerless. In this case, we simply tell all the workers to go home. That's hundreds of thousands of people without paychecks. They're not at work doing their jobs, and they don't have money to keep food on their tables and the economy humming along.

Also, government contractors, including military contractor probably, are not getting paid. Same effect economically, plus you eventually erode military effectiveness. At the very least, you erode confidence and build uncertainty about how things are going to play out (as has been the case since the election in 2016.

Also, consider that the Russians have been hyping their new hypersonic weapon. Timing is interesting.

The rule of law is further eroded because there's no Attorney General. There's no secretary of defense.

Remember how no one in the MSM wanted to use the word liar and then the word treason? We used it here from the beginning, the MSM followed. Tin foil hat snugly in place. Anyone want to call this a coup?

Emptying out the government, effectively shuttering agencies, refusing to nominate diplomats, appointing unqualified people to executive and cabinet posts.

Elie Wiesel said: "It happened so fast."