myself i run my radbox in another room. (no fans in my PC so nice an silent) ( have 10 ft of hose connecting to it)
my system is quite as complex as yours however i can't see the flow being so low.

instead of ripping the system apart. start with dividing your system into 2 loops..
check the flow of the first loop,,, and then the second loop.
find the slower loop. then split that in 2.
it will be the fastest way to figure out in which block your loosing your flow...
unless you have to very restrictive blocks in each loop.
my 2 cents