Do XP boosting items affect Exp. Share when calculated

The participating Pokemon only get experience once. Everybody else in the party gets half of the total each.

Experience gain is independent of participants and number of Pokemon in your party, so yes, your party gains more experience overall if you have more people in your party at the same time.

All pokemon earn experience independently. So the rest of your party does not affect the amount of experience they earn. This is also independent of the Exp. Share's on-state.

I do not know how EV's through Battle work in Gen 6. So I won't comment on their distribution here.

So five example Pancham Battles:

Battle 1a (4 party members):

• Pokemon A participates.
• Pokemon A earned 80 experience.
• Pokemon B,C and D earn 40 experience each.

Battle 1b (3 Party Members):

• Pokemon A participates.
• Pokemon A earned 80 experience.
• Pokemon B and C earn 40 experience each.

Battle Example 2a (Exp. Share On):

• Pokemon A and B participate.
• Pokemon A and B get 80 experience each.
• Pokemon C and D earn 40 experience each.

Battle Example 2b (Exp. Share Off):

• Pokemon A and B participate.
• Pokemon A and B get 80 experience each.
• Pokemon C and D get 0 experience each.

Battle Example 2c (3 party Member Exp. Share Off):

• Pokemon A participates.
• Pokemon A gets 80 experience each.
• Pokemon B and C get 0 experience each.

Traded Pokemon do get boosted experience even if they do not participate.

If you equip a Lucky Egg to a Pokemon, the gained experience from EXP Share will be affected by the egg.

For an example, if a normally the participating get 100 exp and the non-participating Pokemon will get nothing, without EXP share...

In Gen 6, with EXP Share on, instead of splitting^[1] the exp amongst everyone, the participating Pokemon would get 100 exp (with no Lucky Egg, the yield 100% of the total exp gained for each participating), while another non-participating Pokemon (with no Lucky Egg, the yield 50% of the total exp gained for each non-participating Pokemon).

Giving the participating Pokemon a Lucky Egg (adds 50% exp), will yield them 150% or 150 exp [100 + (100*.5)], and giving the non-participating a Lucky Egg they will get 75%, or 75 exp [50 + (50*.5)].

A = Participant
B = Non-participant
C = Non-participant
+ = Lucky Egg

No EXP share, no Lucky Eggs:

A = 100%
B = 0%
C = 0%

With EXP Share, no Lucky Eggs:

A = 100%
B = 50%
C = 50%

With EXP Share, two Lucky Eggs (x1.5):

A+ = 150% (x1.5)
B = 50% (x1)
C+ = 75% (x1.5)

_{¹ The item Exp. Share will revert to Exp. All as in Generation I, where when one Pokémon holding this item participates in battle, all other Pokémon in the team receive experience as well. Unlike in Generation I, the experience is not split but rather received by all Pokémon. This means that the participating Pokemon receive 100% experience, while non-participating Pokémon receive 50% experience. Source.}