Whereas he may not have wanted to admit to himself or to you years ago that making moral choices means more than doing whatever you want at all times, this has now become a challenge to him. Times have changed for your father. Today your father's sexual orientation requires more help for him to control.
One constructive way to "deal with it" would be to realize how fortunate you are to have the kind of relationship where your dad cries out for help when he needs your attention. Be supportive, love him for the parent he has always been, and give him as much attention in his time of need as he gave you as a child, so that he won't have to seek out "uncomplicated" attention through homosexual acts.
That is the Spirit of Christ.