I've been there too. I know that sigh all too well. We did end up at CT and they were great with us. They DO NOT cast in mold anymore. It's all computer generated.
My child adjusted so quickly to the helmet. In fact it was a non issue with her. It was mom who had a harder time, guilt. I dreaded the looks, while I did get them and questions I just answered them directly and she looked very cute! Then you will get the people who will say my child had one and look at them now. Always made me feel better. I'm now a person who tells others our story too!
There are so many reasons for the flatness and most are out of parent control. My baby was a preemie and was incubated for a period time and we just couldn't get the flatness to "pop" out. I was a tummy, turning crazy lady.
My child had the helmet for 3 months and I remember at the end I was like, how silly I was for the anxiety...it was really no big deal and over so quickly. We joked that if she ever gets a compliment on her head she had better thank her parents! Is is perfect no, but did it improve yes and no one can now tell only a trained head person (hee, hee).
My great nephew was suggested to get one and they did not have the money for it and you can see it with out a doubt. He is now 4. Is he a happy, healthy, smart, handsome boy - you bet. My husband and I wonder if he'll get picked on by peers as he gets older - so awful, but a reality. My husband was no for the helmet until he saw my nephew.
I had never heard of the fluid flow issue - more guilt :). I would ask your pedi about that.
Not sure if this was helpful or not two/three sides to all situations. Approach all with a sense of humor and a grain of salt. You're the mom follow what you think is right in your heart.