(Adds death toll since start of talks, chemical weapons)
* U.N. voices fears for town of Yabroud
* Bombing and shelling may precede ground assault
* Families flee across border to Lebanon
* Peace talks in Geneva make little progress
By Stephanie Nebehay
GENEVA, Feb 14 (Reuters) - Thousands of people have fled a rebel-held town in Syria after it was bombed and shelled in an...