I had a similar problem trying to make enough flow and have the reactor working.
When I had the reactor connected to the eheim just a trickle would come out of the spraybar and I had bad circulation before that.
What I wound up doing is using an external pump to drive the reactor but I got some black pvc pipe and made a spraybar the entire length of the tank and put it near the substrate. This way I could add the holes to spraybar exactly where I needed more flow and co2 is injected at the bottom of tank, I can't even really notice the spraybar either.
I think a lot of times it's challenging to get the whole reactor system primed, it can be stubborn, I find it helps to use a funnel and just dump water down the intake tube while the pump is running, also try turning the reactor upside down a bunch.
Some people install bleed valves which seems useful. I think sometimes when you just get a trickle, the reactor system is not properly primed. Not too sure though