I agree with LizzieAylett, I think the board that the cake is sitting on might be too thin, and moving it would shift the dowels.I always use the 1/2'' or a cake drum for wedding cakes or tiered cakes.
Meringue powder is a pastuerized egg product, there can't be much difference between the two. If you don't have meringue powder you can use egg white.
Usually 2 tsps of water plus 2 tablespoons of water makes 1 egg white.
This link might help you.
I had a similar issue, I made a 3 tier cake the night before for a wedding the next day,when I took it out of the fridge the next morning I noticed a few imperfections so took some of the leftover buttercream lathered it on and smoothened it out. When I took a step back and looked at the cake I noticed that the bc that I had just applied from the bowl was yellowish compared to the one that was already on, so I made a mental note to always beat the bc again before...
Here's another one with ganache by Linda Harden on cake masters, It is a free lesson, worth watching, but you will have to register.
Ceri. Dz shows how to cover a cake with royal icing, you could apply the same technique, refrigerating the cakes to firm up the buttercream, he does use a long ruler for the top.
Here's the link: http://www.youtube.com/watch?v=1PbOkVa_-38&list=TLdgmxYTLjvxJInYlBR-KGA1ATu-DEer4I
Have you checked out Jennifer from cup a dee, I love the way she presented her video.