I've seen a similar thread slightly further down, but my DS2 doesn't have a dummy or anything like that. he bawls for me (gut-wrenching shrieks while shouting Mummy) If I go in, he howls to be picked up. we sit in a comfy chair in his room, and he goes back to sleep. when I try to put him down he immediately wakes up and the howling starts again. if I bring him into my bed he wakes up and starts having a giggle (much to DH's annoyance) DH settling him has slightly better effects.
I don't begrudge him the comfort and reassurance if this is just a phase, but worry about setting up a long-term habit which will stop him from sleeping independently.
Really I think these phases come and go and it sounds like he has slept independently before so not going to ruin your nights forever. Just persevere, settle in the dark without speaking, no taking anywhere else in house, put down when settled, I usually keep me hand on mine to reassure i'm still there and either wait till gone to sleep or sneak away eventually takes a shorter time or she will go back in cot not on me......
Sure he will eventually start to settle quickly, or will be so tired one night just sleeps through and the pattern is broken. (for a few months!) Anything else attached to muslin, toy he would like to cuddle?