A Paladin with a low Charisma (let alone one with negative modifiers) doesn't make sense to me. Since Charisma is the Paladin's primary attribute, many of the Paladin's special features hinge upon having an above average score. This includes turning, lay on hands, and smite evil in addition to divine grace. Only spells are modified by Wisdom, and having a Cleric as one of the classes seems to reduce the importance of the Paladin's utility with spells. Since spells would be the only non-penalized ability, which is covered better with the cleric, why not pick a straight fighter? If you're having the Paladin just to eventually get the holy sword, I would wonder if the overall effectiveness would not be better with a Paladin with more appropriate stats to really get a better use out of the special abilities of the holy sword. Having a negative modifier might be calculated into the saving throws, but I'd imagine it wouldn't. The intent of the effect is to improve the Paladin, and low scores would nullify the boon and make it a wasted option.
You are correct about the Monk and Paladin. There are other orders, each with different classes that are permissable, but it wouldn't matter if you started as a Monk and Paladin and only took 1 level. However, for the first class you pick, you need make sure the next class allows the previous class to get it, and no Monk or Paladin order allows the other class. For example: None of the Monk or Paladin orders allow either class option, so you have to choose which Monk or Paladin, but you shouldn't be able to play both a "Monk" and a "Paladin."
What will also happen is that with three classes, you'll eventually create an experience point penalty. If you're playing a high powered game and intend to play HOF, this won't be much of a deal. Otherwise, I wouldn't think either the Monk or Paladin (especially with a low Charisma) offers enough benefits at first level to make an experience point penalty worth it for me. If only getting a single class, I'd pick Rogue (which gets the most skill points at first level), or Fighter (an extra feat) depending on what the racial favorite class was.
Since your current combination shouldn't be possible to have Cleric/Paladin/Monk due to the Order restrictions, I'd suggest Monk based on the low Charisma, but I'd recommend ditching both Paladin and Monk for Rogue or Fighter.
senex wrote:<snip>
Correct. Just make sure the alignment is lawful good.You can start as a monk1 then go M1/Pala1 and then M1/Pala1/ CL X. If you make the Cleric a Painbearer you could later add 1 more level of Paladin ( of Ilmater) but adding more then 1 non-caster level will often cause the caster to lose 1 spell level.
I have not tried this. Just from what I read, it suggests that none of the Monk orders allow Paladin, and none of the Paladin orders allow Monk, but since being a Cleric "Painbearer," that would limit the options to the Monk Order of the Broken Ones if it also includes Paladins of Illmater. Either way, unless senex has done so and can testify to it, you'll know as soon as you advance to the next level and try selecting the next class. Only classes that are still eligible will be among those you can pick, and you would need to be Lawful Good as mentioned.