the solenoid is optional and not completely essential correct?
Correct. You will only lose the ability to control it via a timer.
the paintball adapter is for the pin push? I always thought it was for converting thread sizes
My mistake; I was writing that quite late at night. Let me clarify:
The most common ones are ones that will depress the pin and convert to CGA320. There is no on/off, so you need to attach the converter to the regulator, and then screw that onto the cylinder. As you screw it down, the pin will get depressed. Do not screw the adapter onto the cylinder alone, as the pin will get depressed, but you have nothing to hold the gas back, and it will just escape.
There are other adapters that will depress the pin, and also have an on/off switch. You could look into these as well.
also, there is a big valve on the front of the regulator and a black valve on the side of it (the black one on the left side of the picture), are these two valves not adequate?
I am not sure which big valve you are talking about at the front of the regulator. Are you sure you are not talking about the adjustment handle?
The side valve that you are discussing must be removed.
The parts that must be removed are boxed in red. You need to replace them with a needle/metering valve.
here is the regulator I have, under design features it says that it is equipped with a needle valve
The needle valve that is supplied (the parts that were boxed in red in the above picture) is likely not suitable for our needs as it will not allow for fine enough control of the CO2 flow.
Also, I noticed from the specification sheet, that it has a CGA170 connection by default. You will want to replace this with a CGA320 stem and nut as well.
Finally, after doing all this, you will need to ensure that the regulator is in full working condition. I have never converted a regulator that was originally made for natural gas (the CGA170 standard).