How you split the volumes depends always on your work capacity and adaptation to work load, period of the season when that load is planned, related to the goal , availability.
for example – beginning of the season 5x12km and 1x 30-40km ( less km per day , more times per week and a longer run, easy to manage with work schedule of a person that works 35-40 week, to raise volume and intensity
-3×20 and a long run, more rest days, better for someone that has more experience in running, someone that works in shifts and can not train everyday.
– have a microcycles of load ( working weeks that go from 7 days to 10 days), microcycles of rest ( weeks of lower working load that should show up on your plan in 3 to 3 weeks or 4 to 4 weeks.
– Respect the 10% load increase , and never increase load and intensity on the same microcycle.
– use recovery methods , myofascial release, static stretching massages…etc
– Rest day , a rest day is a day that we let our body recover and be prepared for the next week, for an athlete that has no experience , should be a full rest ( nothing related to running) or active rest (a easy walk ) , for an experience athlete , a rest day can be an easy run or also a full rest ( depends always of the objectives of the periodisation and the microcycle in question .
-Where you put the rest days, depends as I wrote above, on the goal ( 1ex . longer run this week is going to be really hard and my athlete has been doing a lot of intensity, I want him to be fully recovered for It… rest day on the day before.
2ex this is a normal week with a longer run, the objective was to raise volume , no rest day , and before the rest day , he will still do a easy run to remove the metabolic product produce by the long run , and then a rest for a better adaptation .
I think that what you are on the right path , but you should respect the rules mentioned above to avoid injury (especially the 10% rule and the rest weeks)
I hope I could help with my answer …