Sorry you're having a rough go! With an older baby, you want to use your voice more than actually PU/PD. You only PD if your LO stands up in the crib, otherwise choose some soothing, reassuring phrases and use those to help put your LO at ease. My preference is "You're ok, you're just going to sleep, it's time for bed." but whatever works for you.
The other thing is, don't go in unless your baby is actually crying. If he's just babbling/laughing/singing let it go. It might get on your nerves ("GO TO SLEEP!") but it's not really doing him any harm and he'll learn to settle himself.