Brand new to Leica. On a whim I bought a Leica CL with a Russian 50mm f2. I got my first roll back and I'm hooked. These are all on 400TX and shot at, or close, to wide open. I was shooting with the giant Canon DSLR kit and had the Leica in my pocket. Obviously I need to practice focusing, but oh oh oh. Nothing like this has come out of my digital files. I wish I had taken more!
Welcome to the forum- you nailed the focus on the last shot.
The Jupiter-8 is a faithful copy of the Zeiss Sonnar. Coming from an SLR to a rangefinder can take some getting used to- mainly as everything looks in focus through the RF. Once used to it, can be easier to focus for fast lenses than a manual focus SLR.
Brian has good advice. Try practicing on the CL and by trial and error you can figure out how it focuses when wide open or close to it at a measured or closely estimated distance..... YOu could also conduct a crude test by mounting on a tripod and focusing on a tape measure at various distances and f stops...to see how the lens reacts.