The problem is that they wouldn't get caught by Kamui. There speed would prevent them from ever being caught. If they were in Kamui land the they might be SoL unless Sasuke's power can rewrite reality like I theorize. Your question is silly though. Its like what if Kakashi got hit by Night guy? How does he survive? They don't get hit that's how.
Second part. Obito has a limited time frame on how long he can hold Kamui intangibilty. 5 minutes I believe, simply hit him with a barrage of attacks lasting for five minutes like an enton rasenshuriken TBB that covers a multi mile radius. I don't think Obito would have the speed to slip out of a multi mile radius attack like that within his 5 minute duration nor would he warp himself into kamui land before the attack detonates. 2nd eye wouldn't be able to warp an attack that big either and if he did, his kamui land would be covered in enton making intangibility out of the question.He might be able to use 2nd kamui eye though and create a space around which he can not get touched by the enton, but by the time it is fired, his entire body will be in Kamui land making his eye unable to warp anything in the real world.