There isn't such a Graft in any book, but it's one likely to be allowed by a DM. As for the spells, only Divine Casters are prevented from casting spells that oppose their alignment (and even then, you can be a LN/TN/CN and still cast both Good and Evil) - my DM house-ruled otherwise, but RAW it works.
I understand only divine spell casters are limited to spell selection by alignment, but your build is a paladin which requires you to have a good alignment. Casting a spell with the evil descriptor is an evil act. I just wanted to point out that not all DM's will allow a paladin to committ an evil act on a daily basis without alignment consequences. I know I could not get away with it, otherwise Devil's ego would already by on my arcane list. Now if you were neutral and got the paladin spell list added to an arcane class's spell list (chameleon, eldrich master PrC from dragon 280), then you would be fine.
We ran into a similar situation recently where a good aligned character with exalted feats wanted to shapechange into a pit fiend, which would bestow the evil subtype on the character causing all kinds of problems. Regardless of alignment, you still count as evil if you have the evil subtype type for spells and effects.
As for the graft, I just got all excited and hoped there was one. My character could use another +2 ;-) Which reminds me, if you don't mind looking like a nightmare, Horse Shoes of the Flame from savage species is great. It grants a +10 Int, +6 Cha, +2 Dex all as unlisted bonuses and grants perfect flight. One, I would pay double to make them slotless since you don't have hooves. Two you need to follow that up with a use magic device check to emulate race (horse). I have used that on a psion character and it was great. Results may vary for spell casters that don't have still and silent spell.
On a side note, does anyone know a way to add a school or type to an existing spell. It would be great if there was a way to make a spell transmutation in addition to its normal school for ability enchancer. Or if you could apply one of the good spell feats to strip the evil type from the spell. It has been something I have been thinking about for awhile, but assume is not possible. People would have figured it would for mage armor and Abjuration champion if it was possible I think.