.Why does Locke have a bandaged hand and a black eye?
Could of had a fight with his dad

.Why did the Others all put on gas masks outside if they were moving out right then and if only one person was tossing a gas can into Kate's room?
In the Q 'Why was Jack knocked out for so much longer than Juliet and Kate?' As you see I think that there is 2 gas cans near Jack. And they might have even gassed Sayid.

.Why were Juliet and Kate drug clear out into the jungle (at risk of running into Smokey) but Sayid and Jack were left at the Barracks?
To bond with Kate so she wouldn't get left behind again .. hmm

. Why were Jack and Kate groggy when they awoke from the gas attack, yet Juliet popped right awake?
No idea.

.Why was Jack knocked out for so much longer than Juliet and Kate?
If you look carefully while Kate goes to get Jack, she opens the door and the creepy music sounds. You see 2 gas cans next to what seems to be some pillows, some broken glass and a wheel of some sort. Look carefully.

.How did Juliet know the locations of Jack and Sayid at the village without searching around?
As folie said, she knew they were there, as part of the plan. Or she thought they were still there even after they had left the village.

.What is scattered all over the floor in front of Jack when he comes to with Kate? (and WHY was the house so messed up and the front door open?)
Looks to me as bullets. Assuming you mean to the left of the picture. Or to the right of Jack.

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