Do you feel like this is all teeth? Are you medicating before nap time to see if it helps? (prob not all naps, do watch the dose guides)
You are not breaking trust because you are right there with him. If you feel better to pick him up then do so. If his teeth are really really bad he might be better having a nap or two in arms.
Is there a chance he needs a slightly longer A time or a shorter/longer WD perhaps? If he is crying this much at nap time I'd be tempted to put him down 10 mins later to make sure he is tired.
With picking up, you might find it possible to pick up only slightly from the cot, to lift his weight off the mattress bad feel your hands on him but not bring him right up to a holding position. The more tired he gets the more you can aim for this (ie start with a full pick up and cuddle). I found this helped my DS once, he was literally at the stage of falling to sleep the second I picked up so I only picked up a cm, he fell asleep, put down he woke, picked up he fell asleep a cm from the mattress, put down he woke and cried, put my hands under/on him and made sure he felt them but without picking up and he was so exhausted he just nodded off. It's tricky to describe but perhaps you get the idea and just see if something like that will help along the way with your own methods when you are trying to sooth him.
Are you using a key phrase? Key phrase is very helpful for verbal reassurance at this stage if you are not shushing.