Hi Luc
My experiences were with the similar low pressure Spraymaster, and I was using a 100psi portable at the time and with One Step.
Firstly, the supplied Spraymaster jet was an 06. A large jet is necessary because of the flow required to draw up the stock solution concentrate. The smallest advised, which I used, was an 03.
With One Step and the Solution brand, so I presume other micro splitters are similar, they perform best when lower volumes of the solution are used. I found with the Spraymaster, like yourself, that I was using far too much product, so after a while I went back to a pressurised sprayer. Worked perfectly for me.
As for your stock solution, I can't advise, ask Prochem. But remember, the stock solution is further diluted by your Hydroforce sprayer in use.
The Spraymaster had four different models. Low pressure and high pressure, plus variable dilutions via a dial or fixed dilutions varied only by different coloured/size restrictors.
Safe and happy cleaning

Ken