Okay so about trad stuff on umbra (exange 3 enchanted item to a new one) i havent be abble on hundred of try to get a eastern sword or a armor breaker one, so if someone can confirm if you can or can't get one that way

also can you get one of those item with 2 effect, like for example +5 speed and 3 dmg, like you can with elf sword for example

cause with dozen of farm session on ???? (the tentaclen entitiy no luck even if i have found at least hundred of them)

finally about great sledge hammer

do the debuff of armor breaker is stronger than ignore protection ?

As you suspected, you cannot get either of those weapons(eastern sword and armor breaker) from the exchange. If those items were available in the exchange, then they could receive 2 enchantment effects.

If the item you receive from the exchange is considered to have a unique enchantment, then it will not be given any additional effects. Otherwise, it has a 70% chance to have 2 enchantment effects, and the other 30% have only 1 enchantment effect. Enchanted items from any other source will only have 1 enchantment effect.

Some gear comes with bonus stat effects even if they are not enchanted. The elven sword comes with  +1 Agility, and can be found at the exchange with 2 more effects. Note that some bonus effects cannot appear twice on the same piece of gear. So the claymore will only ever have 1 enchantment effect, since the -3 speed effect overlaps with the speed enchantment and weapons only have 2 possible enchantments (damage and speed).

The entire pool of exchange items has a total weight of 159.5, and the rarest items have a weight of 0.5 (making the odds of getting one 1 in 319). The weight for Living Suit (tentacle underwear) is 1, and the weight for Living Armor (tentacle armor) is 0.5. So the fact that you found so many is surprising, but Living armor has a unique enchantment and cannot receive any more effects.

The question of the better armor piercing is a complex one; given that only the last 3 bosses drop the Armor Breaker, it's not clear that there is any value to this analysis. Still, it's an interesting question.

The Great Hammer ignores all protection(percent damage reduction), but is still affected by armor(flat damage reduction). The Armor Breaker ignores up to 8 armor, but is still affected by protection. No enemies have protection by default and it is only granted by equipped armor, which is restricted to non-monsters and is subject to enemy types and RNG. Higher level enemies and guards are more likely to receive armor and better armor. 

Leather armor is the most common for weak enemies. Chain Armor is the most common for tougher enemies; though occasionally they get plate. Ninja and Rogue armor might rarely show up on medium and high level bandits. Enemies can also receive enchanted armor items, which have a 1 in 7 chance of providing 2 to 4 additional armor.

Leather: 3 armor, 20% protection
Chain: 6 armor, 40% protection
Elven Chain: 5 armor, 35% protection
Plate: 10 armor, 60% protection
Rogue: 8 armor, 45% protection
Ninja: 30% protection

Enemy base armor (before gear) can be anywhere from 0 for wolves to 40 for giant crabs. The majority of enemies have between 1 and 15 armor.

In mid to late game it's not unusual for people to have 6 to 10 strength and level 5 to 10, which gives us a rough base damage range of 25 to 40. The Great Hammer gives 10 additional damage, and Armor Breaker gives 9 additional damage. Both weapons can receive the damage enchantment. This means that both weapons deal basically the same raw damage (the Great Hammer can deal 1 more). Using our base damage range plus 12 for approximate damage gain from either weapon, we get 37 to 52 damage.

With all this  data we can finally break down the results and figure out what is the best armor piercing. There is only one clear cut winner: magic, as it is affected by neither armor nor protection thus making it superior to both items, especially with mind blast dealing max health as bonus damage and can be used every other turn. The runner up being Aimed Strike, which only has the downside of a 4 turn cooldown, but similar to magic skills is not affected by armor nor protection. With the three abilities: Acid Spit, Mind blast, and Aimed Strike; it's possible to continuously attack enemies without ever being affected by any defense.

Okay, back to the actual results. As enemies without gear do not have protection, this would make the Armor Breaker superior for fighting animals and monsters, with the typical advantage being 4 to 7 damage (Hammer has 1 higher damage). Though the max gain of the Armor Breaker is 8 damage, many of those enemies will have more than 14 armor or have gear that provides protection. However, because armor is applied after protection, Armor breaker increases in effectiveness when the enemy has protection (so long as the damage after protection is higher than the remaining armor). The formula to calculate the  effective raw damage bonus is "ArmorBypassed / (1 - protection)"; but if the remaining armor is higher than the damage then the bonus is 0. We can use this to calculate the bonus for various levels of protection.

20% protection: 10
30% protection: 11
40% protection: 13
60% protection: 20

We can use the damage range from earlier to approximate the amount of damage that could be blocked by protection.

20% protection: 8 to 11
30% protection: 12 to 16
40% protection: 15 to 21
60% protection: 23 to 32

While these numbers would appear to be similar, the important thing to note when comparing these 2 sets of values is that the first set is a flat rate whereas the second set is a percent rate. Thus the general conclusion should be that the Armor breaker is the superior weapon for people  with low attack damage(less than 5 strength) and the Great hammer is the superior weapon for people with high attack damage. While the Armor Breaker deals more damage to enemies with low protection, this weapon is generally not acquired until very late game when there is far less trouble with and incentive for attacking enemies without gear.