Well, all of those ideas are certainly worth a shot…
Not sure how you are going to get any of those spells cast while it’s clawing and munching at you, or breathing acid on you. Distracted spell casting is generally a bad thing; usually worse than distracted driving, but at least as potentially fatal.
But you are welcome to try. I might suggest bringing some bodyguards. Maybe the Abyssal equivalent of Barbarian Demons, Cleric Demons, Mercenary Demons, Thief Demons etc. A regular adventuring party that can protect the wizard trying to cast all these spells.
Here’s the real thing…dealing with a dragon is every bit the problem as dealing with a greater demon. Look at all the work the Rod had to go to to have a chance at killing Tom and his mini-demon horde. They used mana absorbing spells and all sorts of things, plus a big nasty knight. Still didn’t work (almost did).
In either event, in the Planes of Man, to perma-kill a demon, you basically have to keep it from returning to the Abyss. Over the centuries, wizards and clerics have figured out various ways to do this, if they happen to be prepared and get lucky.
It seems logical that one could do the same for dragons, certainly on the Planes of Men, and probably something in the Abyss (we just don’t know where they are fleeing too in this case, which complicates things).
The problem is, no one that I know of has ever tried. You’d have to be really committed to it, and prepared to take a lot of casualties.
I suppose some of the demon princes might know how to actually do this; maybe some have. They just aren’t telling me.