About portfolio, we try to give new user experience in our portfolio template. With our portfolio template, you can use our built-in filter function to show portfolio list with certain category. Because of that we are not using default archive template which is currently use for blog.
Regarding to your questions 1 & 2 which is related, it needs some customisation to make it possible. But, we will consider it (portfolio archive & category links on single portfolio) to be enabled on Jkreativ on next update.