Fever during pregnancy can cause neural tube defects, congenital heart defects, orofacial clefts, miscarriage.
It's great that you care so much about the infinitesimal risks of acetaminophen. You should care 100x more about these risks that are 100x or 1000x greater.
Walking 12 miles is not only uncomfortable, it is also higher risk to Mom and baby than driving.
You have to balance all the risks and benefits.