How should a layman react?
What are we to do?
Have you been fasting and doing penance for a positive and fruitful outcome of the Synod?
Have you offered your Holy Communions for this intention?
Have you offered a rosary for this intention?
Have you been staying in the state of grace and praying for this intention?
Have you offered your time to teach catechesis or marriage prep in your parish or diocese?
Are you instructing your kids, or those youth within your reach, as to the truth and meaning of marriage and human sexuality?
Are you doing any of the above? Do the best you can and strive for more.