Most boys train after their 3rd B-days. Once he turns 3, start the process again.
Have a bedtime routine: Brush teeth, read him a short story,
say "Twinkle, twinkle little star", say a prayer and shut off the lights.
At this point, he should really be falling asleep on his own. Yes, you should be letting him cry it out. It takes a few days. Yet, many parents today cannot stand hearing a child cry.
At age 3, many fears surface and it is hard for a child to fall asleep. Try to get him to fall asleep on his own now. If you do decise to sit in the rm, do not say a word. He needs to do this on his own.
Make sure he is playing , running, etc for a bit after you get home for work.
One night I went to the store and my husband let her cry it out. He had no problem w/ it. It worked. It does not harm the child. You wlll be thankful you did it.
Do not let him watch tv before bed. It's too intense and not a gd habit.
Try providing white noise like soft classical music or a fan noise, etc...in the background.
An hour and a half nap might be all he needs if he can't fall asleep at night. Have them get him up first.