The Ferber method may upset your son more because you are going in the room. With extinction, you don't go in. It may seem tough but some babies get more upset if you go to them.
For us, going in at intervals made it SO much worse. It was so hard, but really the longest she ever cried was an hour off and on (never solid - she'd cry for a minute or two, stop for five minutes, cry for a minute) and really only the first night.
It sort of sounds like you've done this...I would work on naps first. My daughter sleeps a million times better on nights she gets good naps. Sleep really does beget sleep.
If you can get him to nap, that might lead to better luck with sleep at night.