Chainmail Bikini Games has a nice PDF on Paladins called "Call of Duty". It has a very extensive commentary on the Paladin's Code. It might be worth looking at.
In some ways, the Code should be very strict. In other ways, there should be some leniency. Not a lot of leniency, but a little wiggle room that leaves the Code open to interpretation. Suppose a Paladin has Answered the Call and placed his Faith in a single God, something that is not required to be a Paladin. Suppose the Paladin is in a predominantly LG realm. Now, if the Paladin's Church has the same ideals as the Lord of the Realm, but differs in how to pursue those ideals, which Authority is more legitimate in the Paladin's view? Situations such as that should be left up to the judgement of the Paladin, so long as they remain consistent. If that situation ever came up, it would be an interesting RP experience for the player, and if you back off the code a little to allow them to make the decision w/o a penalty, you will probably see some interesting character development.
I don't think you should really pursue a point system. After all, intentionally committing an Evil act is an automatic out. If you do want to go with a point system, you should probably sit down with the player and provide examples of "bad conduct" beforehand. Otherwise, there may be differences of opinion that could be avoided.