Is spell dmg worth at high levels?

[MaxWilson]

Just to make sure I follow right:

Bob has 32 max HP.
Bob takes 37 damage (maxHP <= current damage < 2*maxHP), and is knocked out.
Bob succeeds at his first death save.

5E RAW: Bob is at 0 current HP with 1 success and 0 failures; not stable until he gets to 3 successes, or rolls a nat-20 death save and recovers to 1 HP.

(A) MaxW rules: Bob is "at -5" (but really "at 5 damage above max HP"). As a result of "on a success you stabilize", he's stable. (Yes?) If so, taking any non-fatal damage just restarts the 6 HP (32/5, rounded down) "bleeding" per death save failure, until he succeeds a single death save?
(B) Does a nat-20 death save do anything "special"?
(C) If you're stable at damage >= maxHP for some amount of time (the same RAW 1d4 hours?), do you wake up with maxHP-1 damage?

(A) Correct, correct, and correct. He dies at 64 damage.

(B) Natural 1s and natural 20s don't do anything special, unlike RAW.

(C) Yes and no.

Yes, you wake up eventually. I will even let you retain consciousness at damage >= maxHP, if you want to mumble weakly or something (IIRC I usually ask for a DC 10 Con save to keep consciousness if you want to), even though you'll still count as Unconscious for purposes of auto-crits and stuff. But on second glance I see now that's not what you're asking about.

No, you have to heal normally somehow to regain HP, which means either an external healing source or resting***. There's no accelerated healing which pulls HP out of nowhere just because you were knocked unconscious--you're better off healing while you're still healthy.

*** I also disallow short rest healing unless you have a bard with Song of Rest, and on long rests you can either regain half your HD or spend some HD, but not both, both of which tie into the "wounded warrior" scenario (see below) as well as "wounded enemy" and "wounded mate of an frenemy" and things like that. I want wounds that last for days, not 1-4 hours.

Ahh okay thanks for explaining, I use Roll20 for games, so I just let the individual tokens manage the hp (I input the total, then I can just type '-20 ENTER' and it'll do the math for me, auto updating the character sheet if it's a PC).

How do you find this has affected the overall difficulty of the game?

It's hard to say, because it changes behavior: without pop-up healing to rely on, (most) PCs just try to keep their damage low in the first place, or mitigate it by healing before or between combats (sometimes during combat too, but long before nearing 100% damaged). I do occasionally read about people doing things like leveraging familiars to give people healing potions for popup healing, and those things don't work at my table, but to know how much those things actually affect the difficulty of the game I think you'd have to ask them, not me. Like, does embracing pop-up healing via familiars and potions that let you take on significantly tougher monsters, or is it just way of preventing individuals from winning the Darwin Award and making the player sad? I never see pop-up healing so I can't really say.

For me it primarily affects (improves) the verisimilitude level and my suspension of disbelief, and my ability to design scenarios that include things like finding a near-dead warrior in a ditch with vital clues--that guy's not just at 0 HP and in need of a Healing Word (1d4 hours away from regaining 1 HP), he's at 80 HP over his damage maximum, and would be dead if he weren't such a tough old geezer. He needs, like, a dozen healing potions or several days of bed rest if you don't have magic.