Morality as Mere Instrumentality?

As part of my Moral Philosophy course, I have been reading some Thomas Hobbes and a contemporary proponent of contractualism, David Gauthier. There are a number of issues that have been raised in these writings and should cause some concern to the Catholic Christian. I will frequently on Filioque elude to, and explicitly state a few of some beliefs on deification and it is pertinent that I relate it to this topic.
In Hobbes, human kind is constituted by a desire for self-preservation and a hope for a comfortable life. But in the 'state of nature', which is war of all against war, man is unable to rest secure, without the fear of being attacked, his goods stolen or his life ruthlessly taken. To counter this miserable state of suspicion and mistrust (a living beside, but not as a community), man makes a social contract with those around him, so that he may pursue his desires which is the final cause of such negotiation. Through the contract he will have to constrain and restrict himself in maximising his utility so that his 'neighbour' may obtain his good, i.e his self-preservation and a comfortable life, and in turn his fellow man will permit him the same. The rules and conventions which are produced, could never truly be called morality as they exist (human-manufactured) for the sole purpose of reaching the selfish requirements of man. This is rightly called 'instrumentality'.
For the Christian, the commandments of God are not impediments to fruitful living, nor are they simply to be endured. Rather, they are a fundamental aspect of the constitution of the true human person. They reflect the unity, harmony, justice and love of the Lord. Man by following these 'commands', does not bind himself to a mere duty that he must perform for the sake of said duty, but it is through striving to attain love and the focus on Christ, Who supremely did the Father's will, that man is made like to God. The laws which state that man must serve God above all else, no matter what emotional attachments he possesses, manifest the truth that humanity can only properly delight in the God Who made it.
Can we say that the commandments are ends in themselves? Not particularly, but they have their force and coherence as reflections of the harmony of the intra-Trinitarian life. By clinging to these statutes, man is led away (often unwillingly at first) from the diverse concerns and preocupations that threaten his wholeness, to Him that is Life, the Source of all being. But neither can we say that the laws of God are merely to be used as stepping stones. The faithful son of God fulfills these commands by a complete subjection to God, and it is only through this that the dictates can be accomplished. These commands cannot simply be altered to meet present demands or modified to the latest trend as it is through them that the human person is conformed to Christ Who is the same today, yesterday and tomorrow. An essential part of this adherence is the complete delivery of oneself to God. In the social contract, although it is wise ('practically prudent') to remain faithful to your covenants, the heart of man may stand aloof, cursing inwardly. Such is not acceptable for the son of God, as the Creator knows the depths of man's being and our incessant grumbling. Man being willfully torn asunder can never hope to share in the divine life.

'Lord, who shall be admitted to your tent and dwell on your holy mountain? He who does no wrong to his brother, who casts no slur on his neighbour...he who keeps his pledge come what may...such a man will stand firm for ever.' (Ps 14/15)