What archetype of monk are you taking?
Far Strike Monk and Zen Archer will both give you relevant bonus feats, but neither of them will allow you to flurry with a crossbow.
And you can't combine flurry with Rapid Shot/Manyshot. It is its own full-round action.
So your attack sequence is actually +6/+6/+1 with Rapid/Manyshot, and you can't use Feinting Flurry.
Furthermore, Manyshot won't apply your sneak attack twice, so it isn't a priority for precision-based ranged builds. Greater feint is more important.
I would take two levels of Far Strike Monk and flurry in both ranged and melee with daggers. Upgrading one dagger as your primary weapon in melee, and then buy disposable daggers to use on ranged attacks. And at BAB +6 you could take Improved TWF which would apply to your flurry. Granting you the same attack sequence in both ranged and melee.
+6/+6/+6/+1/+1
(Flurry, 1 ki)
However, if you want to use a crossbow then you'll need another way to exchange your first attack for a Feint. You could take Zen Archer and flurry with a bow if you don't mind switching to a bow-build.
Alright, ignore that part then.
But you still can't flurry with a crossbow, so unless you change your weapon this build won't work. And I just remembered that crossbows can't use Manyshot. Your best option if you want to combine rapid shot/flurry is to either throw shurikens or take the Far Strike archetype. But remember that you'll be suffering a -4 to all attacks with both activated. Combined with 3/4 BAB, you'll probably miss more than you'll hit.
Slayer's Feint let's you use Acrobatics instead of Bluff to feint, but your Cha mod is +3 so I don't think the benefit outweights the cost.
A monk weapon is a weapon with the monk special quality - take a look at the table here, under the special column. It's not the same as a weapon that a monk is proficient in.
Re Sly draw, it changes the skill used but doesn't explicitly change the action required. Since changing the action to a free action would be a larger change than changing the skill, the lack is probably meaningful.
It's an action of a type defined by your other feats I think, it says they still apply. E.g. if you have improved feint it's a move action.
Oh, so no crossbow to flurry.
Sly Draw says that if i draw a light weapon y can feint, i assume its a free action triggered from another free action (quick draw a dagger). is it not?
The feat is very poorly worded but it is the intent of the author to ONLY allow you to change the skill used to feint. So you'd still need to forgo one of your attacks.
Im focusing on using DEX to feint, cause in early lvls the difference will be a lot since im not planning to buff CHAR.
Let's say you use DEX to feint by investing a feat or two.
The difference between your DEX and CHA mod is only two, so that's the only benefit you get. +2 to feint at earlier levels when you wanted it to count.The bonus will scale as you boost your dexterity, but a simple Skill Focus: Bluff will give you +3 at lower levels and +6 after level 9.
Your charisma bonus is fine. You shouldn't seek to switch the ability modifier used for feinting, but rather get additional bonuses to Bluff/Feint from racial traits, magic items and spells.
Almost every race has an alternative racial trait granting them a bonus to Bluff (Silver Tounged for humans), so that should be an obvious choice.
A Magenta Prism would grant you another +2 (competence) for 800 gp, and if you're not playing PFS then you could add a +5 (competence) bonus to feint on your armor for 1875 gp (would not stack).
But if you're worried that you'll fail 35% of all feint checks against enemies who max Sense Motive (not that common), then you could always take the feat 'Weapon Trick: Weapon and Shield' to be able to take 10 on feint checks.