Is it permissible to say "O Helper," "O Facilitator," or "O Expediter" when seeking Allah's aid, and what is the criterion for this, and what is the ruling on one who says it forgetfully, ignorantly, or intentionally?

It is permissible to say: "The Helper, the Facilitator, and the Granter of Ease," because the intended meaning is Allah, Glorified and Exalted be He, due to your explicit mention of "O Lord" at the end of the supplication, whether you said it forgetfully, ignorantly, or intentionally.