No others exist. What you're waying is that there is, in the most literal sense, no law.
Our Head of State would be arrested as an impostor
By whom?
and physically removed, creating a situation that would need be resolved by an emergency session in the House of Representatives, selecting an interim president.
There is no such procedure in the Constitution, and there is no such thing as an interim president. You are simply making things up.
Appointments, executive orders and signed laws voided and Biden, as President of the Senate would be an shaky ground for succession. Succession would be decided in the House.
There is nothing shaky about the succession. It's in the straightforward black-letter law of the 25th amendment. There is no provision for the House to choose a president at any point except the lack of a majority in the Electoral College.
A Constitutional Crisis arises with a defective executive and a warring House and Senate and a muddled Supreme Court.
No constitutional crisis arises, because SCOTUS and Congress aren't stupid enough to force it to that point.
I really don't think you've thought through this scenario. The a priori assumption is that someone -- SCOTUS or someone else you haven't specified -- has the power to at a single stroke unseat a president and void every act of Congress for the last few months. Then this entity can simply make up new rules, declaring the vice president ineligible for no clearly articulated reason and appointing the House to choose a new president because ... well, I guess an American Idol style cell-phone vote wouldn't be dignified enough.
If any person or persons are able to exercise that sort of authority, then the Constitution is wholly void. Rioting in the streets isn't the issue -- those rioters will have as much claim to lawful authority as anyone else.
I'll get the Caterpillar if you get the bucket of water.
If Obama was ineligible then he did not legally get a majority and neither did anyone else. Biden did, but only as Vice-President, not as President.