Even Nethack, the most capriciously malevolent roguelike known to man, never actually renders itself unwinnable through sheer chance.
100% of nethack games are unwinnable. (rounded to the nearest 0.1%)
Also I don't get what's so bad about acid. I'm gonna crunch some numbers and figure out just how much damage one can expect to take in an acid bath. Editing this post with stuff later.
EDIT:
The maths and spacial reasoning behind my madness. Spoiled for post-shortening reasons.
(Keep in mind that 1 damage is 2% HP)
Acid appears to do 6 raw damage.
It's halved to 3 if you're running.
Then foot armor and TaN is subtracted, so 2 armor + running = 1 acid damage.
Berserk makes you so incredibly resiliant that acid becomes 1 and lava becomes 3, even without armor.
Most doors in an acid bath will be surrounded by acid:
..#..
.=#=.
.=+=.
.=#=.
..#..
Because all doors can be shot down, this will result in 2 turns of acid damage per door.
Many small rooms will be covered in acid, but large rooms will remain (mostly) acid free.
All barrels in an acid bath are acid barrels. As such, destroying a wall using a barrel results in this:
....#..
..===..
.=====.
.=====.
.=====.
..===..
....#..
So this makes inter-room travel a mere 1 turn of acid damage, provided you can risk fighting everything in the room at once.
You'll cross about 5 rooms before finding the stairs, making it 8 squares of acid on average before you get to some stairs.
Anyway, if you bothered to read that then traversing between rooms will require you to run through 1-2 squares of acid. I'm assuming there's enough barrels to blow up every wall, so it should be more than possible to avoid acid-flooded rooms and stick to the (relatively) danger-free ones.
If you have a medpack, run the whole way, using the medpack to extend your run. Even without TaN and boots you'll take 72% damage at a ludicrously unlucky maximum. (52% cause you used a medpack)
If you have an envirosuit, use it!
If you have protective boots, acid does 8%. 2% if you run. Think of a quick path through.
If you find any powerup on the way, ANY powerup, you'll live. Berserk reduces acid to 2% damage, invulnerability to 0% (No really?). And a heal will reset your run, if it's only a health globe.
The only complication is trying to get 100% kills, items and levers. For that you'd need to be better prepared than just a single medpack.