I think they are interesting as they are. To prevent misuse (using the power to damage undead), you could change the wording around a little. Maybe like:
Great Healer
Benefit: You are able use Lay on Hands to heal an additional amount of HP damage per day equal to 2Xlevel. This extra amount can only be used to heal injuries and has no effect on undead beings.
The Faith Healing would be a fine feat, but it seems like it could just as easily be a house rule that it is the normal way a Paladin's healing works out without having the Paladin spend a feat.
As for the Vow of Humility, how about this:
Vow of Humility
Prereq: Sacred Vow
Benefit: When using Lay on Hands to heal wounds, the amount of hit points healed is 50% greater than the points of Lay on Hands used by the Paladin. This effect only occurs when LoH is used for healing and not to inflict damage upon Undead.
This solves most of the arguments against the feats as they were originally writteny that have been made so far while not causing a problem should the Paladin decide to use LoH for damage. I also think they keep in line with the original intention of the feats.
I like Notmousse's ideas, but I dislike having to spend a feat on them. Instead, LoH could be redesigned so that instead of hit points healed, the Paladin can sacrifice a number of LoH hp to reproduce a spell-like effect. 3hp of LoH per spell level. So, a Paladin could spend 3 LoH hp, and instead of curing 3hp, it has the effect of a Remove Fear spell. Or spend 12hp of the LoH total to Neutralize Poison. And you could limit it so that the Paladin can only produce the effect if he were a cleric of equal level trying to cast the same spell. This would prevent a 3rd level Paladin with a 20 Cha and a +2 Cloak of Charisma from spending 12 of his 18 points to Neutralize Poison (something the party cleric wouldn't be able to do anyway). To prevent abuse and also keep the Paladin from overshadowing any cleric in the group, I would allow him to do this for a limited number of spells that the Paladin chooses. Maybe 1 spell per even or odd Paladin level.
This does have the effect of making the Paladin's ability to Cure Disease even more useless, but that could instead be worked in to the LoH, so that at 6th level, instead of getting it 1/week automatically, the Paladin now has the option of choosing it as one of the optional effects in addition to any other spells the Paladin chooses to reproduce by spending LoH points.