Is there a way to uncurse items when playing as a berserker guys? I can rip off one but I'm unable to remove the others.

keep trying. unless perma-cursed (very rare) you will succeed eventually

[21:53] HugoV: Improved The Glaive of Pain (9d7) (+10,+30) for 4480 gold. You are wearing The Glaive of Pain (9d7) (+10,+30).
[21:54] HugoV: I wonder how this cost was decided

That's quite a cheap cost, which didn't make sense considering the high score of The Glaive of Pain. Because of this, I decided to stop using The Glaive of Pain.

On the other hand, upgrading Sting at this Fighters' Hall is much more costly. Interestingly, cost of upgrading Narsil or even Careth Asdriag is the same as the Glaive of Pain.

Even weirder: cost of upgrading my Cap of the Fell Rider is like 7.7k for a single upgrade...

Also, race abilities i.e. via 'U' command aren't blocked by Anti-Magic, right? Should they be blocked by Anti-Magic? :)

This is not a bug; you're probably used to the cost of enchanting both to-hit and to-dam at the same time. In this case, you're only enchanting to-hit; and the weapon score evaluation algorithm gives a fairly low weight to accuracy, especially for lowish accuracy values of up to 10. (The value of a single point of accuracy more than doubles at +11.)

How about these unpopular ideas:
Make Destruction destroy stairs and destroy floor items beneath player?

Destroying under the player doesn't make sense, and destroying stairs can mean a list game for an Ironman character.

Questionable Virtue Workings
 

Not necessarily a bug, but perhaps disagreeable design depending on your view:

Line 3946 in object2.c, the Sacrifice virtue actually reduces the value of generated gold piles if it has a positive value; thematically, this arguably checks out, but mechanically, it's punishing the player for being "a good person". Only calling it to your attention in case you feel differently than about how it's currently working.

Also, I'm pretty sure I've mentioned this one already at some point, but for posterity the Patience virtue currently has similar functionality; it actually increases natural monster generation if it's in the positive, decreasing monster generation if it's in the negative. Unlike Sacrifice, I can't logically understand this one (also Patience is actually really hard/tedious to get and keep a positive value for; to be punished for actually doing so further makes no sense).

? of Acquisition
 

So what is the ideal time/depth to read these? I'm continually disappointed in what I'm getting from them.

My current Hermes Rogue, CL 37, got lucky and had stockpiled 7 of them. So when I got to the bottom of Battlefield (DL 50, my deepest current dungeon) I decided to go wild and read all 7.

The result: nothing useful at all. A rod of lightning ball (of holding, whatever that does). A Fur Cloak of the Bat. Small shield of Elemental protection (FiPo). A Hell Harness. Dwarven shovel of extra attacks. Best item was Double Chain of Celestial Protection (LiCfCa) but its not something I can use. And a Scythe of Slicing of Sharpness.

So what does everyone else do? Hold onto them for deeper? Read them at DL 90 or something like that?

And am I the only who thinks their results should be more special?

Use them when you find them. The amortized value of just one more GREAT drop goes down with dungeon depth, as GREAT drops become more and more common. That said, it's a little more complicated in multi-dungeon variants, where your depth is not so uniformly increasing. If you find it at a shallow depth in the wilderness, wait to return to your previous level. (Or just sneak into the edge of the mountains or the like.)

For a stack of them I'd go to angband level 1 or so. Back to Telmora(?). Then Trump Tower to Angband level 98. Bring !enlighten and ?destruction and recall. That town service costs a lot. 100k iirc.