Now, the worst case scenario here is where he would remain in this present condition, where, like Terri Schiavo, despite responsiveness, he'll be declared "vegetative" and they move to murder him.

In which case he’d be a martyr. 
p.s. My “reliable source” is a priest who has seen him. 

I was at the Hospital with Bishop Williamson by his bedside till the night (still in pallative care) yesterday.
I won't share all the details as I am not in position this early to say anything, but I will say all the disinformation on twitter has been disgusting. Such a distinguished Pious Bishop should not have lies let alone a false announcement of his death

Everything I am thinking here is pure speculation but some things can be deduced from the tidbits we are given about his condition. (especially the note Matthew posted from Fr Chazal)
The bleed must not have been large enough to displace brain tissue to the point of herniation of the brain stem. That would have been a worst case scenario. He still has meaningful and appropriate function, albeit minimal. Is the bleed reabsorbing? I suspect when and if he is stable enough he will have further scans of his head to see the direction that the hemorrhage is taking and if there needs to be more aggressive treatment. In a younger man  they would remove part of the skull for increased bleeding ( temporarily) to relieve the pressure of the hemorrhage, but I don't know if Bishop Williamson would be able to tolerate that at his age or if they  would even consider it. In the old days they did burr holes but many times now depending on where the bleed is they thread a catheter into the brain under flouroscopy and are able to drain it that way. Minimally invasive techniques.
  Hopefully the bleed is stable and regressing. That would be the best and most hopeful place to be. 
Apparently he has movement on both sides - nobody mentioned paralysis so that's good.
I guess when he is stable or slowly improving within his critical state, they will soon have to address basic needs, like IV nutrition via a central catheter and eventual weaning from the ventilator ( Being on the ventilator at all is just a given assumption on my part- I can't imagine that he is not)
If he cannot be weaned from the ventilator, after a week or two they will consider tracheotomy. That's usually the course. It doesn't have to be a permanent situation, it's just that the ET tube down the throat does a lot of erosion after that point and needs to be removed and the access  site changed.
As far as medications they will medicate him for pain but not too heavily as not to compromise function, and maybe give him anti-seizure meds IV as a precaution.
Outside of maintaining acceptable vital signs and general monitoring, it will just be a matter of observation and waiting.

This is all speculation on my part and what is going through my head at this moment. Don't take it too seriously. Just a dim roadmap to possibly flesh-out the situation.

I was at the Hospital with Bishop Williamson by his bedside till the night (still in pallative care) yesterday.
I won't share all the details as I am not in position this early to say anything, but I will say all the disinformation on twitter has been disgusting. Such a distinguished Pious Bishop should not have lies let alone a false announcement of his death

Thank you for the post.  So, I think most of the disinformation all leads back to the same source, that one post.  I was on the fence about whether the post was made by someone who had reacted emotionally to the prognosis of His Excellency's imminent death with a certain amount of despairing cynicism, conflating the prognosis of certain death with death itself ... or whether it was made by some wicked hateful individual out of malice toward Bishop Williamson and/or his "followers" (i.e. those who care about him).

I did a bit of digging and found that the original post was made on a site called telegra.ph ... and this leads me to believe that the post was malicious.  So, this would appear to be a domain set up PRECISELY to be falsely associated with the well-known Telegram, similar to how phishing scams work ... except that on telegra.ph, anyone can post anything with complete anonymity.  So the deliberate intent to remain anonymous, which intent is contradicted by the content of the message where the poster lists that lady's name (i.e. if you wished to post anonymously for a legitimate reason, you wouldn't put your name on it) ... suggests that it was done by a malicious troll.

So, the next question is whether it was done out of an evil hatred for Bishop Williamson, hoping that it would dissuade people from praying for his recovery, or for the slightly-less-evil intention of trolling those who genuinely care about His Excellency by creating chaos and havoc among them.

At the end of the day, I smell a Jew ... given that His Excellency is most hated by them, whereas it would only be other Traditional Catholics who would even understand much less disagree with the nuances of a theological disagreement that to an outsider would be entirely incomprehesible, and no Traditional Catholic would pull such a stunt.

As a friend of mine here will attest to, I hope they are putting drops/ ointment in his eyes as well, for if he recovers we wouldn't want him to suffer from dried out damaged corneas either. That is a whole other ball of wax to contend with.
Hope someone in England reads this.

Yeah, american doctors are clueless.  "Well, we don't have a test for that, nor a drug, so there's nothing I can do." 

I have years of experience where doctors almost NEVER even look for, much less are able to find, the actual underlying root causes of varoius symptoms.  Per the Rockefeller allopathic medicine in the US (not sure about UK), they don't dig too deep, but there's also a presssure from the business side of medicine where they don't want to take the time to look into things too deeply.  5-minute visit on average increases profit margin.  You have this symptom?  OK, well, try this drug and if it doesn't work make another appointment (so we can charge the insurance again).  And then of course, the next time you visit many weeks later, the context of the entire visit is lost (despite some cryptic and probably illegible scratch notes they may have made in your file).

Of course, I'm speaking here more about the false pretentions of certain knowledge here, where they really have no clue about how certain things work.  If you dig into even some of the drugs they prescribe, you'll see on many of them that the "mechanism of action is unknown".  They have no idea how it works.  While not really knowing how various complex body functions work, or how certan disease progress, they nevertheless copy this air of certainty, having created the perception of authority and knowlege by donning the white lab coat.  They've been "studying" cancer and cures for cancer, with untold billions of dollars at their disposal, and still don't really know how it works or have any idea how to cure it.  I won't digress, but that's because they're philosophically excluding the most likely causes of cancer right out of the gate.

If he is just in palliative care, they will not be doing anything to treat him progressively- just comfort measures and maintenance. That's what palliative care is. Maybe they can change that status if they see he is improving on his own- I don't know.
Forget my post above. He will not be getting any aggressive treatment on palliative care.
If I were sitting in the room I would be careful to monitor the pain medication. He may be on a morphine or versed( midazolam) drip, especially if he is on a ventilator. Palliative care is into pain management.