I like your wapo article roussette, but I think they might have made some assumptions.
1. Trump orders Attorney General Jeff Sessions to fire Mueller. Sessions quits, as does Deputy Attorney General Rod J. Rosenstein and Associate Attorney General Rachel Brand. Eventually someone agrees to fire Mueller. Republicans either will not pursue impeachment or are obliged to begin impeachment hearings but refuse to vote out articles of impeachment. In 2018, Democrats sweep to victory in the House and gain a seat or two in the Senate. Trump cannot be removed (two-thirds of the Senate is required for removal), but his presidency is in tatters. Some aides or ex-aides face criminal prosecution.
If we get to the 2018 mid terms and the republicans haven't done anything about mueller being fired, it's unlikely that the mid terms will be fair and free, and so dems sweeping to victory isn't guaranteed.
2. Trump orders Attorney General Jeff Sessions to fire Mueller. Sessions quits, as does Deputy Attorney General Rod J. Rosenstein and Associate Attorney General Rachel Brand. Eventually someone agrees to fire Mueller. Republicans, together with Democrats, pass by a veto-proof majority an independent prosecutor statute. Before impeachment proceedings can finish, Democrats sweep to victory in 2018 in the House and gain a seat or two in the Senate. Trump cannot be removed, but his presidency is in tatters. Some aides or ex-aides face criminal prosecution.
Not sure why sessions would quit as he's shown no compunction in violating his supposed recusal when recommending comey to be fired but I suppose it doesn't really affect the rest of this scenario. Dems being victorious again not guaranteed.
3. Republicans join Democrats in warning Trump not to fire Mueller. Mueller remains and keeps digging. Mueller subpoenas damaging documents; Trump refuses to comply. A court orders him to comply. He doesn’t. We have a full-blown constitutional crisis.
Not sure that they will warn him off firing mueller in any meaningful way with repercussions, although it might be a pleasant surprise. Some have expressed disquiet but republican media, wh staff and some repubs have been pushing the narrative that it's fine if he pardons himself.
- Resignation
I think this could happen in theory, but trump has had a tendency to double down harder when challenged. The scope and gravity of this situation might make him decide resigning is better but he's done so many things that have been damaging to him that it isn't a safe assumption that he'll pursue the most sensible option.
5. Republicans join Democrats in warning Trump not to fire Mueller. Mueller subpoenas damaging documents. Trump complies. The evidence of collusion and/or obstruction is overwhelming. Mueller recommends prosecution or impeachment. The GOP turns on Trump, who is impeached and removed (with the GOP by that time possibly in the minority in one or both houses)
This is the one I'm hoping will happen but I'm not sure that trump
Will allow mueller to continue unimpeded.
I don't have alternate scenarios of my own, but I do think the potential for authoritarian measures is being underestimated.