Q: How many identical acks need to be received for fast retransmit to occur?
The DUPACK threshold is a configurable parameter. Linux uses a threshold of 2 (sysctl: net.ipv4.tcp_reordering).
Q: Name one of the men described as "The Father of the Internet."
Apparently, Leonard Kleinrock is also one of the fathers of the Internet: http://www.cs.ucla.edu/~lk/.