In order to keep your CO2 in the liquid state at that pressure, the temperature needs to be at least -9 degrees Celsius or lower. Any warmer and the CO2 is just gas. The other factor you need to consider is the density of the liquid CO2 and the optimal solvent density for extracting terpenes.
Both have low boiling points. Might be challenging to separate your terpenes from your ethanol if you don’t have the right rotovap or distillation setup. On the other hand, works great for your heavier fractions and plays right into winterization.
These are low pressures even for subcritical co2. Would be a long extraction time depending on your input weight and the yields are still not that great, however, the quality is legit.
I understand though that this is your limiting factor. At 850 - 1000psi, your optimal temp should be around 14 - 17 degrees C. This plays into the solvent density again, specifically targeting your heavier compounds like cannabinoids.
Start playing around with different pressures and temperatures ON THE COMPUTER OR ON PAPER. Although you are trying to find parameters that keep your CO2 in the liquid state, they also affect the density of said solvent. Terpenes have an optimal range of solvent density for extracting and so do cannabinoids.