Check out Steve's article The Fundamentals of Bodyweight Training on Eatmoveimprove.com for the hows and whys on programming bodyweight workouts,also I would recommend his book "Overcoming Gravity" as well for better training info.
If static holds: Planche, front lever, and back lever are your goals, then putting them into your routine can help you develop them faster. However in my own experience, focusing on too many goals at once will slow an scatter your progress. I have had dramatic strength increases with Steve's training advice on gymnastics, as well as narrowing my goals. For the front lever I realized a few months ago that I was not focusing on proper scapula position and lat activation, as well as a proper hollow body. I also performed bodyweight rows by pulling with my arms, instead of focusing 100% of proper scapula retraction and lat activation. Fastforward to this week and I my full lay front lever has gone from 1-2 seconds ( on a good day) to a solid 5. Moral of the story? Master the basics, and think about what your doing. Simply doing a pull-up dosent mean your doing it right, you have to focus on using your scapula and activation your lats.
Read Steve's article, buy his book, really it will help your training tremendously.
As for your question, no that is not entirely correct. If your max L-sit is 20 seconds, using the 50% method, you would do 6x 10 seconds. This brings your total L-sit volume up to 60 seconds. This is okay and works well for some. I like using Steve's variation of the Prilepin's Table, which takes your total static hold time, and allows you to adjust your sets and reps based on %'s of your static hold, similar to weightlifting. In 2 years of bodyweight training I like this method much better. Using higher hold times helped me go from a 2 second tuck planche to a 20 second tuck planche in 8 weeks. If Steve wishes to detail that chart he may, but since it is from his book I will not.
Based on your schedule I would adjust to a total body program, 3x a week. This can be done M/ W/ F or Tu/TR/Sat, etc. Handstand and L-sit/manna progression should be treated as skill work in the beginning. This means you would do them everyday, after your warm-up, but before your strength training. Static holds for the planche, front lever, and back lever would come next, Then concentrics like dips, rows, pull-ups,etc. Make sure to include pre-hab as well. Reverse hypers and core work should be done at the end of your workout.
Again, read Steves article, heres the link.