I agree with all that as a matter of one way of presenting the logic of stating that pleasure is the alpha and omega and all that. However in the end the logical statement comes back to the "feeling" of pleasure which is not something that can be uniformly defined for all people at all places and all times. So i think it's necessary to be very careful once you engage in this as a logical debate. Apparently Torquatus thinks that his position on this is better than that of Epicurus, which I think should not be accepted at face value.
QuoteSome members of our school however would refine upon this doctrine; these say that it is not enough for the judgment of good and evil to rest with the senses; the facts that pleasure is in and for itself desirable and pain in and for itself to be avoided can also be grasped by the intellect and the reason. Accordingly they declare that the perception that the one is to be sought after and the other avoided is a notion naturally implanted in our minds. Others again, with whom I agree, observing that a great many philosophers do advance a vast array of reasons to prove why pleasure should not be counted as a good nor pain as an evil, consider that we had better not be too confident of our case; in their view it requires elaborate and reasoned argument, and abstruse theoretical discussion of the nature of pleasure and pain.
And as to the issue of instrumental or practical end, which is the "greatest" end?