Unfortunately, as you have found out, these needle valves are not really meant for the fine adjustment of gas flow that we require in this hobby.
You are better off getting a quality needle/metering valve for this purpose.
I have reserves against those all-in-one pressurized CO2 setups, but some people swear by them.
Thanks, after actually experiencing the inconsistencies, all of these people's post about the same thing finally have sunk in. Looks like it's time to start looking into a legit co2 set up. I don't want to skimp on this tank at all, it's become my pride and joy.
(it's the one in my signature)