I have been your plan through and it looks generally quite fine out.
I found a single error, where your test estimates were set to a half marathon time at a marathon distance, but it is fixed and has not moved significantly on your zones.
Some of it, which means that you must run a very slow Z1 is that you have to get used to the marathon distance. When you run the marathon you need to reinforce some slow fibers, which takes over when the rapid is tired. Why are some of the best marathon training is a combination of the speed of the fast zones with slowly running on the Z1. Mentally you need to see if you can give it full gas by Z4 and, in turn, enjoy that you can run really slowly on the Z1.
You can assess how Z4 fits you when it should be going strong?
You have at the same time, put a very narrow band at the min and max 3 days. If you are open for a 4th day gives it more opportunities, but it is quite understandable if the week does not give room for the 3 days plan is still the most important optimizes training to you.