--is sex between a husband and his second wife a blessing?
Of course it is. But marriage is only for this world. And all the pleasures of marriage serves the purposes of God to ensure the generations. If you are asking about a second marriage after unwarranted divorce, the divorce is a sin that must be repented of. You must consult the scriptures and get counseling to see if sex after the second marriage is a sin. I am not studied in this area.
Something of the Scriptures that I just read and came to mind:
Matthew 22:23-33 (NASB)
23 On that day some Sadducees (who say there is no resurrection) came to Jesus and questioned Him,
24asking, "Teacher, Moses said, 'IF A MAN DIES HAVING NO CHILDREN, HIS BROTHER AS NEXT OF KIN SHALL MARRY HIS WIFE, AND RAISE UP CHILDREN FOR HIS BROTHER.'
25"Now there were seven brothers with us; and the first married and died, and having no children left his wife to his brother;
26so also the second, and the third, down to the seventh.
27"Last of all, the woman died.
28"In the resurrection, therefore, whose wife of the seven will she be? For they all had married her."
29But Jesus answered and said to them, "You are mistaken, not understanding the Scriptures nor the power of God.
30"For in the resurrection they neither marry nor are given in marriage, but are like angels in heaven.
So if according to the RCC, Mary is the wife of the Spirit, is she still that after her death?
Mat 19:7 They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away?
Mat 19:8 He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so.
Do you actually think God can glorify His Name through you and not His Mother in the supernatural things that He did for her? It doesn't matter whether you or I believe it or if Zwingli and Calvin and whoever believed it, truth is truth; regardless.