Voldemort -- Needing some insight

I've started writing Lord Voldemort, and I was wondering how the Deatheaters would address him, particularly Lucius and Severus.

'My Lord' came to mind. I can't see them addressing him by name. Too disrespectful.

Also -- approximately when did Voldemort start taking on a snake-like appearance? Anotherwords, when did he start looking oh, not so humanish? I know I'm not wording this as best as I could, but give me a fuckin' break, eh? It's 3 am here.

What is the best approximation for the year that Tom Riddle was born?

maeglinyedi -- since you write quite a bit of Voldemort, might you lend your expertise?

Anyone is welcome to add their two cents by the way .

--P