I am now using 2 needle valves. I have better control now, but find myself making adjustments daily. Really annoying. Definitely appreciating my main tank's 60 dollar dual gauge. Money well spent. I wish they would make a dual gauge that directly attached to paintball tanks - other than that 150 dollar red sea one- which looks cheap regardless of the price.
Searching the web for a high pressure fine adjustment needle valve seems hopeless.
PS- I am sure EOTD do happen, Co2 is deadly to fish/shrimp/snails and caution should be exercised when using any co2 setup!