Is what happens between an engaged couple—touching, looking, and talking about marital life—considered "zina" (unlawful sexual intercourse) punishable as such, and will Allah bless this marriage?

The suitor is a non-mahram (a man not in a prohibited degree of kinship), and it is not permissible to sit with him or speak to him without a need, or to exchange glances, let alone touch. All of that is impermissible. For a suitor to touch the hand of his fiancée is a figurative form of zina (fornication/adultery), and it is a sin. "The zina of the hand is touching," but it is not actual zina, and its ruling regarding sin and punishment does not apply. The foundation of marriage should be the fear of Allah and avoiding disobedience to Him.