How does Absorb Spell (Su) work? [Spellthief class]

Absorb Spell (Su) is a class feature of the Spellthief (Complete Adventurer variant, p. 13) and it reads as follow:

Beginning at 7th level, if a spellthief makes a successful save against a spell that targets him, he can attempt to absorb the spell energy for later use. This ability affects only spells that have the spellthief asa target, not effect or area spells. A spellthief can’t absorb a spell of a higher spell level than he could steal with his steal spell ability (see above).

To absorb a spell that targets him, a spellthief must succeed on a level check (1d20 + spellthief class level) against a DC of 10 + the spell’s caster level. Failure indicates that the spell has its normal effect. Success means that the spellthief suffers no effect from the spell and can cast the spell later (or use its energy to cast one of his own spells known) as if he had stolen the spell with his steal spell ability. His normal limit of total spell levels stolen still applies.

At 20th level or higher, a spellthief can choose to use the stolen spell energy as an immediate action (see page 137), either to recast the original spell or to cast one of his own spells known using the stolen spell energy.

Let me pick these two phrases:

  • if a spellthief makes a successful save against a spell that targets him, he can attempt to absorb the spell energy
  • To absorb a spell that targets him, a spellthief must succeed on a level check

So, in order to absord the spell, you must succeed on a saving throw and then pass the level check.

What I do not understand is this part:

Failure [on the level check] indicates that the spell has its normal effect.

Does it refer to the fact that the spell complitely affects you even after a successful save?

or

Does it mean that if the spell’s descriptor has somithing like “Saving Throw: Reflex half” then this halved damage (or effect) still applies?

May a spellthief cast a stolen spell using a metamagic rod?

Spellthiefs (Complete Adventurer variant, p. 13) can not apply metamagic feats to stolen spells they posses.

The Steal Spell’s description reads, in part:

A spellthief can’t apply metamagic feats or other effects to the stolen spell unless the specific spell stolen was prepared with such an effect. For example, a spellthief of 6th level or higher could steal a wizard’s empowered magic missile, but only if he specifically chose to steal empowered magic missile. If he chose to steal an unmodified magic missile, he couldn’t steal an empowered magic missile, a silent magic missile, or any other metamagic form of the spell. A spellthief couldn’t steal an empowered magic missile from a sorcerer, since the sorcerer applies metamagic effects upon casting and thus has no prepared empowered magic missile spell.

Does this description refer to metamagic feats in general?

Would it make any difference to apply a metamagic feat through the usage of a metamagic rod?

Is there a way to add both Knowledge (religion) and Knowledge (the planes) to the Spellthief skill list?

… Other than taking Skill Knowledge twice? (or Skill Knowledge + Apprentice)

I’d like this character to enter Ur Priest at level 6, so he needs max ranks in Knowledge (religion) and 5 in Knowledge (the planes), neither of which are class skills for Spellthief. And both feats are also going into qualifications. (Yes I know the Otyugh hole could give Iron Will or flaws could give bonus feats, but those are inelegant.)

As a human, the character would have spare feat for adding the two as class skills. Is there a feat that could pull that off?

Or, is there a race that would make them class skills by default? Or for that matter, a race that gets one of them as a class skill and one of the feats I need as a bonus feat?

Steal Spell-Like Ability (Spellthief) vs once per day Spell-Like Abilities

Assume that we have a Spellthief with Steal Spell-Like Ability (see here) and a willing creature, a unicorn say, from which the Spellthief wishes to steal a once per day spell-like ability (say, cure moderate wounds) that the willing creature has not yet used. Assuming that the willing creature never uses its once per day spell-like ability, is it possible for the Spellthief to steal and use said ability more than once per day?

As I see it, the arguments in favor are:

  • The ability’s description says “A spellthief can use a stolen spell-like ability once

  • Spellthief suck, so a permissive GM might allow it regardless of RAW.

As for the arguments against:

  • The descriptions says For all purposes (caster level, save DC, and so on), treat the spell-like ability as if it were being used by the original possessor of the ability and it can be argued that this may include not being able to use the spell-like ability twice in one day, or it may even prevent the willing creature from using the ability after the Spellthief has used it (due to it arguably counting as the creature having cast it).
  • This seems awfully exploitable, so a GM may rule against it regardless of RAW.