The CMC should allow you to shoot something 32 mm wide full frame by itself. The problem is that your LX100 is not a very stellar macro shooter. Adding a + 7 to the CMC should get you to something like 30 mm full frame (not a big improvement). The SAGA +25 will get you by itself to something like 30 mm full frame (a bit more than the CMC). Unfortunately the physics of your camera are the fundamental limitation to shooting something that is 4 mm across.
A lot depends on your focus distance needs. Once you get beyond +15 or so the biggest worries are DOF and can you find the critter. I think the CMC is very well designed (at least for my macro lens) and is quite nice optically. I haven't seen the Saga but always worry about CA with such lenses.
A few weeks ago, my wife and I went to Maluku Divers to do a photo seminar/class with the Underwater Tribe. Mike Veitch and Luca Vaime led a group of 8, 7 photographers and my wife the videographer ( who has listened to the f/stop, aperture story for the 20th time and keeps asking what an f/stop is) for a week of diving the muck sites of Ambon. The class was held at Maluku divers and Joe and Emily showed us great hospitality, good food and lots of great diving. Over the course of the week, we had seminars on basic shooting, advanced techniques, some basic Lightroom classes. The classroom teaching was very good, Mike is a great teacher and Luca did a fine job on the Lightroom side, but it was in the water that made this class very special. On each day Mike would take 4 of us and Luca the other 4 and worked hands on with each student during the dive. Unlike almost any other photo class, neither Mike nor Luca took a camera into the water, only a slate. They would help us think about what to shoot and how to shoot it and they did lots of looking at our pictures after they were shot, writing furiously on the slate to change this or that and try again. One thing that we worked on quite a bit is how to use high power LED lighting instead of strobes or as backlighting for shooting larger critters. After the diving they were available every day for photo critique during the afternoon when we were not diving. The diving was typical Ambon with several Rhinopias in varying colors, lots of nudibranchs both common and relatively rare, lots of hairy shrimp, one green shrimp (the very tiny one), and tons of other muck critters including the very hard to shoot shrimp that lives in the blue tunicates. Overall, we had a great trip and want to thank Joe and Emily for running a great operation, and Mike and Luca for helping us all make our pictures better and for making the whole week great fun.
Yes it can be done, I wrote a short article that is on the Optical Ocean Sales blog site about it. Of course you can do it, using relatively bright LED lighting but you can't capture action and will have little DOF control.
-2 to 2 stops on flash compensation is not manual flash control, at least in my opinion since 2 stops is only 1/4 power. Yes you can use TTL mode on the YS03 and it will work some of the time. The reason that I would like to have manual control (I too use the strobes on manual even though the camera is doing TTL) is that after a few shots at full power the strobe recycle time on the camera gets long, presumably because of heat concerns.
I don't think any camera that can set an S value in A mode, that's why there is manual mode on the camera.
You can get c-clips from McMaster Carr, but I would call Scott at Bluewater and see if he has one or at least tell you what size it should be. On my EM-1 housing, the fn1 shaft is 2 mm diameter and the total width is 3.9 mm suggesting that the correct c-clip is