KILLINGWORTH, Conn. — As the financially struggling Boy Scouts sell off a number of campgrounds, conservationists, government officials and others are scrambling to find ways to preserve them as open space. A $2.6 billion proposed bankruptcy settlement designed to pay thousands of victims of child sexual abuse has added pressure to an organization beset by years of declining enrollment, and the Scouts and their local councils have been cashing in on their extensive holdings, including properties where some of the abuse took place.