A) I plan on stretching my paycheck to almost last all month.
The statements B), C) and D) all contain a split infinitive but is the first one the one that most needs to be revised to eliminate a split infinitive because it creates confusion. A better statement could be: I plan on stretching my paycheck to last almost all month.
because compound sentences with coordinating conjunctions In this case, the sentence must contain a comma before the conjunction for correct punctuation.