Yes you're right. 3-way, 2-position valve is what I'm trying to find out more about now. I will post some found options for further feedback. It's been very fruitful to see your discussions and then to see a solution emerge.That was becoming apparent.
Let’s clarify for the sake of the OP, as their posted schematic will not work, and the introduction of a dump valve alone, or with the indicated valve, will not work.
To be honest, after 40 years of Millwrighting throughout industry, I too am confused about the terminology. It does appear though, that industry standard counts ‘ways’ as ports, and positions as potential spool positions. I see a / appearing, and have run into foreign manufactures using different terminologies, but NA usage has been standard, in my experience.
With that being said, I recommend that the OP consider replacing the indicated, 2 way, 2 position valve, with a 3 way, 2 position valve. If a quick dump action is desired, include that as well.