Skald Spell Warrior and Weapon Song

[GODIN Frédéric]

Hello !

I'm looking for answers on the way "Enhance Weapons" is working

Enhance Weapons (Su):

At 1st level, the spell warrior can grant a +1 enhancement bonus to the weapons (including ammunition) of allies within 60 feet. At 5th level and every 5 levels thereafter, this enhancement bonus increases by 1. The maximum bonus gained is based upon the number of weapons affected: +5 to one weapon, +4 to two weapons, +3 to three weapons, or +2 to four or more weapons. Fifty pieces of ammunition count as one weapon for this purpose. The wielder of a weapon enhanced by this raging song counts as if he were under the effect of an inspired rage raging song for all purposes involving the skald's rage powers.

These bonuses can also be used to add any of the following weapon special abilities to the weapons enhanced by this ability: dancing, defending, distance, flaming, frost, ghost touch, keen, mighty cleaving, returning, shock, seeking, or speed. Adding these weapon special abilities consumes an amount of bonus equal to the special ability's cost (see Table: Melee Weapon Special Abilities). These enhancement bonuses and special abilities overlap with any enhancements or special abilities the weapon already has, though duplicate special abilities do not stack. If an affected weapon is not magical, at least a +1 enhancement bonus must be added before any other special abilities can be.

The bonus and special abilities granted by this raging song are determined when the song begins, and cannot be changed until the raging song ends and another is begun. These bonuses apply to only one end of a double weapon.

I've looked around to find similar abilities and of course compared it to the Arcane Duelist kind-of-the-same-but-not-quite Bladethirst ability.
But I wish confirmation on a few points :

1/ The way I see it, the bonus is given to ALL chosen weapons and cannot be different for each ones. It is written clearly in Bladethirst, not here, but it just make sense. Am I wrong about it ?

2/ The limit on bonuses, does it include special properties, or can I go nuts and give everybody in my party a +2 flaming frost shock defending weapon ?

3/ Does that effect include natural weapons ? Once again I would naturally say no, because there are very few effects like that that do, but...

4/ How do feats like "Master Performer" apply exactly to that ability ? Can you raise the maximum bonus on each weapons with them ?

Thanks in advance for any input :-)