VP - you don't need to leave him to cry.
There's a difference between ignoring the crying for increasing periods of time (a technique known as Controlled Crying) and allowing him to cry but comforting him. There is a difference between abandoning the baby (which is what I imagine CC feels like to the LO) and standing by the cot stroking him while he cries. When you try to change a baby's habit and he cries, it is not out of fear or despair, it is anger and frustration because he is not getting what he knows and wants. But you, the most important person in his world, are with him, keeping him safe, so it's OK.
It is very important that he knows what is going to happen next - which is why you set up the same simple, clear, routine for every sleeptime, and establish it before you do anythign else.
If he's rolling in his sleep then the time has come to put the dropside up. You can always put it down again when you go to bed yourself. I think you need to take the mobiles away. They are too stimulating at the moment. Put a couple of soft toys in the cot, so that he may have a chance to 'fix' on one and use it as a comforter. Or you could use a muslin in the same way. Muslins have the advantage of being replaceable!
If you're struggling to spot the sleepy-signs early enough, try clock-watching. My babies could rarely stay awake longer than 2-3h at 6m without getting ratty and over-tired. They usually wanted a nap at around 9am (presuming that they woke 6-7am-ish), and if that was a short nap then they needed another nap at about 12-1pm-ish. If it was a long nap, then they needed another nap at around 2-3pm-ish.