How valid is it to refrain from consummating the marriage with one's wife after the legal marriage contract (aqd al-qiran al-shar'i) and to abstain from visiting her or being in seclusion with her until the official wedding, for fear of the high divorce rates in this era?

Your warning against intercourse before the wedding and your diligence in avoiding privacy with your wife after the marriage contract are commendable, especially if the contract has not been officially documented. Note that documenting it is essential for protecting rights. We advise you to be patient and chaste until the consummation of the marriage. What will help you with this are fasting, safeguarding your hearing and sight, avoiding places of temptation and passion-inducing stimuli, occupying your time with beneficial activities, seeking Allah's help, and frequently engaging in remembrance (dhikr) and supplication (du'a).