1. Weak: Wes's life imprisonment feels like a really long time.
Better: Wes's will spend the rest of his life imprisoned.
Explanation: The really adds nothing to the extent of this sentence.
2. Weak: Nick wants, I think, to go to Gatsby's party.
Better: Nick wants to go to Gatsby's party.
Explanation: Since you're going to support this claim with evidence and since your name is already on the top of the essay, you don't have to qualify the idea with I think.
3. Weak: Blanche's somewhat troubling past comes to light over the whole, long course of her visit to New Orleans.
Better: Blanche's troubling past comes to light during her visit to New Orleans.
Explanation: You're not going to hurt Blanche's feelings by calling her past troubling. The whole, long visit takes as long as it takes, so you don't need to modify.
4. Weak: Iago pretends to be very supportive while he actually plots against Othello at almost every step.
Better: Iago pretends to support Othello while plotting against him at every step.
Explanation: If you make the bolder claims and support them with textual evidence, your essay will end up making a stronger point.