Don't go to hard an your self Boyan. I find your dam idea to be a great one. The only drawback is that you lose the connection between the two sides hence they become two separate world's. I will definitely use this dam technic and will try to use something as thin as a raiser blade. Maybe cut open some beer cans and make some stripes of it. I think a thicker dam material could introduce a small unwanted wave. And as you seem to be nuts with precision you won't want that. :)
Sorry for your second fail but thanks for sharing as it is informative. Now I know it requires 21 degrees Celsius and in my case I see a problem there. In fact it even gives me some confidence as the result you have achieved is better than what I aim for in my build do to the nature of application.
Good luck with your next pour tho, if you go for one.