I would change it to level 2 (as most people stated), and grant the paladin a +4 bonus to charisma. That turns it into a nasty combat spell, that does not lend itself to abuse through scrolls or potions. The duration is what keeps everything in check.
You can't make a potion of a spell with a range of personal anyway.
And the problem with a +4 bonus to Charisma is that eagle's splendor is already a 2nd level paladin spell, so clearly what you're considering is too powerful.
Awesome hell knight avatar by gr8artist!
"I thought you were a hero."
"Heroes are so common these days."
"All of this, it's all because of you! Why are you here?"
"Run home to your Sister, boy!"