There is not technique set for these textures, so they won't compile. Since techsets are a serious pain, I would just pick different textures, or only use two. Unfortunately techsets don't automatically generate in WaW, like they do in CoD4.
2. It is not possible to make streams out of dynamic water, you can only make streams out of textures with the suffix _stream.
It's an interesting area in the job place now, saying that it's one of the most, if not the most competitive areas. Unfortunately, a lot of studios have turned 3+ years of professional experience into a job requirement, which makes no sense whatsoever in the long run. I would say first off, do you have a portfolio? There are many free website hosts where you could quickly throw one together. Main thing about level design is geometry. This is the biggest thing they look at. How do you block out your map's areas, how does it flow, etc. Fine detailing is mostly done by the art team, which is something to keep in mind. Radiant is as good as level editors get, so that's great that you have experience there. Some studios that use Radiant are Sledgehammer, Raven, Infinity Ward, and Treyarch. You can apply to those at anytime, since they are all under the Activision system. The biggest thing is to get a large portfolio, with level type variety. Another thing they look at is team experience, it's good if you have some works in which you collaborated with a team in order to complete. They like this since it is similar in how they work. I'm open to answer other questions and help. I'd also like to see your portfolio if you have one, or once you finish it.