When changing the timing belt on D16A6 or D16Z6, it is very important not to skip any teeth (grooves) on the pulleys of the crank/cam shaft and the belt. It is so easy to do so though. To overcome this problem, it is advisable to mark the old belt's groove and the corresponding pulley's groove prior to the old belt's removal. Then transfer the markings (liguid paper works great) onto the new timing belt. Moreover, don't forget to remove the tensioner's spring when installing the belt, it'll make things a lot easier.
When it comes to changing intervals for the belt, mine did not have any cracks at 137K. But they say that you should change it every 100K. Next time, I'll change my timing belt when it will have 150K on it. As far as the belt tensioner goes, before changing my timing belt at 270K for the second time, I was brainwashed by the internet postings into changing one, where in fact it was not necessary to do so. There was a little bit of a free play on the bearing, but not that much to make it necessary for a change. When changing the timing belt on D16A6, I don't think it is necessary to change the water pump every 100K. I have seen my friend's working for over 230K without any problems.
