I have a theory (well, I'm pretty sure I know what at least part of your problem is, because it happened to me!)
FB are made with pul that has DWR applied to it- waterproofing. They will not wick to the outside very easily because the outside is very water repellant. Regular pul that most people buy is not DWR treated, although you can find the stuff....
I had wicking diapers that I made very similarly to yours. I ended up just buying a spray bottle of permanent water guard and DWR-ing the things myself. Then they worked perfectly for like a year, until the PWG wore off, they started to wick a bit around the legs again. So I re-applied. It was $10 and made me feel like all that time in front of the machine had not been a total waste- it's SO frustrating to make leaky dipes!!!
I'd try it- www.atsko.com
. The permanent water guard is VERy good stuff, not smelly, etc...I found mine locally for like $10.