Is it considered showing off (riyaa') for a husband to give a gift to his wife without seeking anything in return except the reciprocation of love, while also seeking a good reputation along with sincere devotion to Allah, performing acts of obedience to gain Allah's pleasure and the pleasure of one's parents, or for one to transform the intention of a good deed from showing off to sincere devotion to Allah Almighty?

Dedicating something to one's wife out of love is not showing off (riya'). Being keen on having a good reputation is not objectionable; rather, it is an indication of desiring good deeds that earn praise. Your performance of acts of obedience to God and in compliance with your father's command is not showing off; rather, it is a good deed. Correcting one's intention from showing off to performing deeds sincerely for the sake of God is a religious requirement. If the thought of showing off occurs after one has started a deed, and one repels it, that does not harm the validity of the act of worship.