My interpretation of the power-plant question, based on context (he's about to go off with Jack), his flimsy excuse for not applying, and his later remark that in them days he'd just quit the job, is that he wanted more freedom to see Jack.
But back to RT's original question. Jack does offer to help out Ennis financially, and gets harshly rebuffed, that first summer as they're packing up to leave the mountain. Granted, Ennis reacts that way because he's distraught that their time together is ending, and because he's angry that Jack doesn't read between the lines and understand the real reason he's so upset, and because Jack seems so cheerful himself. But Jack seems to take the exchange more literally, which may be what keeps him from ever offering again.
But if he did, I don't think Ennis would have accepted.