you are mixing up different meanings for the word "interpret". "Authoritative Interpreting law" (or in general interpreting law) doesn't mean "trying to understand what it means" but means "deciding what it means in practice"
especially if you add a "authoritative" in the front it in legal language means they gave themself the right (i.e. authority) to decide (i.e. interpret) how law should be interpreted, i.e. what the meaning behind the written word is in practice
this is 100% without doubt or question not compatible with any democracy (including the US constitution) and is pretty much one of the default approaches Dictators use to get unchecked authority
It means that in practice (assuming people comply with the EO) means they can do whatever they want as they can just willfully absurdly, but with authority , misinterpret laws. Including to e.g. persecute judges which "step out of line", or members of the senate which don't vote for whatever he wants etc.
Upon impeaching the President, the VP would become President, and he would order the military to remove the ex-President. At that point the military would have to decide if it's more loyal to Congress or the ex-President.
Because they could just as easily impeach him if he doesn't, then it falls to the Speaker of the House. But if I were them I would just impeach them both at the same time for the same reasons.
And who impeaches a President which just gave himself the right to authoritatively misinterpret the law in whatever way they want and in turn can trivially turn you live into a living hell if they insist too
especially if you yourself could get a part of the pie and don't think it will negatively affect you
I mean don't get me wrong if they would do so literally tomorrow it would work.
But as the majority of senate likely feel they have little to loose it won't be tomorrow.
And when they realize that maybe they won't get part of the pie (they are mostly now useless for him) it will be to late and the fear of repercussions will have set in.
The question of whether you'd be happy to have the other guy do it always applies. If you wouldn't, people moaning when it happens is always a good thing.
Everyone tasked with enforcing a law must necessarily interpret its meaning. The judiciary gets the final say though.