Personally, I'd give up on the resettling. If he only sleeps for 30 minutes so be it. Let him catnap and eventually he'll go longer (mine did 40 minutes naps until they were about 9-10 months).

This will go again the grain here, but I found DS1 would cry a lot when I tried to settle him with bouncing, rocking, swaying, him in my arms (i.e. 40 minutes of crying whilst being held). But if I put him in a darkened room alone he would cry for 2-3 minutes and go to sleep... I know this is a gentle parenting site, but I just followed what worked for my baby and I think it was that my presence is too stimulating for him. Since then, he has always been a kid who will sleep in a cot in a darkened room but will not sleep if there is anything at all exciting going on.