Is it permissible to marry a divorced woman? And does the husband experience intrusive thoughts about her previous interactions with her ex-husband?

You must fight obsessive thoughts by ignoring them, and thank Allah for a righteous wife. Her previous marriage is not a defect; the Prophet, peace and blessings be upon him, married women who were not virgins, other than Aisha. A non-virgin may be better than a virgin, so do not give Satan a way to corrupt your life, and trust in Allah and implore Him to reconcile you and your wife.