Dear Bogdan,
I appreciate your enthusiasm and dedication. I am aware of the amount of effort required to write even a simplest melody of Byzantine chant, not to mention long, elaborate pieces such as this. In fact, composing in this music genre, requires tremendous amount of prior reading, memorizing, comparing, and also a lot of inquiring and checking during the process of composing itself, for each of our chosen melodic thesis.
As we steadily and persistently acquire chanting experience (I am talking about decades, rather than years behind us), shaping a melody to existing templates should become easier, thus making our chanting more predictable, and it's all in predictability for a chanter, as well as for the people who listen. If they don't have to concentrate on the melody, they could pay attention to the words of a prayer. The catch is to make the end of a melodic pattern recognizable by its begging.
I presume you are probably already acquainted with the work of Father Ephraim from Arizona. If not, do not hesitate to visit his page. On his site one might find a handful of useful information and practical guides, including melodic formulas (a tool for anyone who would like to assemble a melody,) as well as a set of orthographic rules.
https://www.stanthonysmonastery.org/music/ByzMusicFonts.html
It is obvious that you are well in the process of learning the chant. You are able to read music. I believe you recognize all eight tones, and various modes for different types of hymns. All you need is, in my opinion, a lot of practice to became an experienced chanter, and that is still ahead. Patience and hard work will bare fruits.
I would love to see more of your Slavonic compositions in the future.