In addition to my question about doing a leak test, is there some kind of cleaning product that should be tried first? I saw a YouTube vid with a lot of views say that cleaning kits were a waste of time due to how small the passageways are on modern condensers and evap.
Why do you think cleaning is necessary? Did the previous owner say that there was that black debris in the lines? Did the previous owner say that the original compressor had seized?
When I replaced my compressor, I used denatured alcohol to flush the lines out, but it probably wasn't necessary because I didn't have any debris in the lines which can be caused by a seized compressor, which I did not have. Yes, I've heard that if there was debris in the lines, that the condenser could be plugged up/partially plugged up and that it's difficult to clean that out, requiring replacement of the condenser. Denso condensers are not expensive online, btw, but you need to determine if that is even necessary.
If the refrigerant is evacuated, you can pull a vacuum on the system and let it sit for a number of hours to see if the vacuum gauge drops. If it doesn't drop, then there are no leaks. Another way to determine leaks is to install a dye into the system and use a black light with those special yellow glasses to find a leak. There is also an electronic device that can detect leaks.
According to the factory repair manual, the total system charge is 17.28 oz +/- 1.06 oz of refrigerant. In other words it should be between 16.22 oz - 18.34 oz of refrigerant.
I can not find a chart in the factory repair manual showing appropriate pressures based on ambient temperatures and humidity. The repair manual does list an A/C pressure gauge set as a recommended tool, but I can't find anywhere in the manual that shows actually using the tool. I believe the reason is that the repair manual advocates evacuating the system and charging with the correct amount of refrigerant (shown above). With this correct amount of refrigerant, there is little need to worry about the pressures (assuming all the A/C components are in good working order). The pressures do indicate the operating condition of the system, though, which is one of the reasons people use them to decide what to do (add or remove refrigerant, repair/replace certain components, etc.). The repair manual has many, many pages, so perhaps I've missed a page, but not as far as I know.