re the parliamentarian's ruling

What the Parliamentarian issues is not a final ruling. It is advice to the presiding officer of the Senate. The Democrats still have the political option of disregarding this advice by a ruling from the chair. If they are willing to do this, it is not as large of a roadblock as it would appear. The question is if they have the political willpower to ignore the Senate Parliamentarian.

The Senate Democrats are just fine with the Senate-passed healthcare bill. Left to their own devices, they wouldn't change it at this point. But the House can't pass the Senate version, because too many provisions, such as abortion, are anathema to enough Democrats to prevent the bill from winning a majority vote. As many folks have noted, if the Senate doesn't pass the reconciliation fixes first, then the House votes are left potentially hanging in the wind, because once the House passes the Senate version, why would any Senator in his right mind exert political capital and risk being seen championing parliamentary dirty-tricks to modify a bill that he's already on record supporting as it was? Say your one of the Senate Democrats who helped force the Stupak abortion amendment out of the Senate version. Why would you, after having done so, then risk any political capital at all to take a VERY tough vote to RESTORE the Stupak abortion amendment? You wouldn't, deal or no deal.

So the House Democrats understand quite clearly that there is no reason to trust the Senate to make the reconciliation changes needed to make the bill more palatable to the House Democrats. That's why the interest in passing the amendments before the Senate bill itself is passed by the House.

Yes, the Vice President can overrule the parliamentarian. That would likely result in a motion from the floor for the Senate to overrule the presiding officer's procedural ruling. Democrats would probably stomach an on-the-record vote that it is appropriate to amend a law which has not yet been passed, but that's going to be another painful sign of their disunity and their willingness to resort to unusual parliamentary maneuvers to pass the bill in the face of widespread public opposition. At least a few Democrats do understand that part of the public's hostility is to the methods they are using... I'm not the only one who saw the Massachusetts focus groups filled with supporters of Scott Brown's opponent who nonetheless agreed that if Brown was elected, Congress should start over with healthcare, as that election would be a clear indication of the popular will.

Here's another wrinkle. What is the risk that the Court would decide that it's not possible for a bill which is not yet law to be amended as proposed through the reconciliation plan? Even if Biden overrules the parliamentarian, what happens if the Court determines that the reconciliation fix is void because it purports to amend a law which did not exist at the time it was passed? The statute would have to be conditional: "If HB XXXX becomes Public Law XXX-XXXX, it is hereby amended to read ..." To what extent is such conditional statutory language valid? Simon, ever see any cases along these lines?

At any rate, how the Court would handle such conditional legislation is another wrinkle that must concern the House Democrats, whose arms must be near about wrenched from their sockets at this point.