Thanks for your reply.
What concerned me was not the meaning of the words but the case. It seemed to me that “magni momenti” was genitive and therefore the sentence lacked an object. So perhaps “rem magni momenti” might be better. This is what I had in mind when I asked whether you had the genitive of value in mind here. Perhaps others will coment if I am wrong here and rem can be understood in the context.
This highlights the difficulty of writing one’s own sentences because of course you have grasped the essential issue of indirect statements but have introduced another grammatical point which distracts from practicing the thing you wish to concentrate on.
Apart from that, why do you think that using the translation excercises from North and Hillard would be better than making up my own sentences (or say, rewriting some dialoges into indirect speech, etc.)? (Say if I found somebody else to correct my sentences.) I am asking because I got the impression that both Minkova as well as most foreign language teachers I know seem somewhat weary of translation as an means to improve language skill (Surely it works, but at least here people are moving away from it and giving more weight to different approaches. I do get that Latin is not modern language with a great pool of spoken native content, speakers, and so on and that might necessitate a different aproach to learning the languge, but I am unsure about the details. Hence my question.)
I would turn to the reply I made to your initial post about improving written style.
"Prose composition books are useful because they review grammar and assist in reading texts by making what is passively known more a part of your active knowledge. The problem with free composition is that your approach is not going to be structured and you will probably be using only constructions with which you are already familiar.
The kind of free composition I think you are interested in is an end goal and you shouldn’t confuse the means with the ends. North and Hillard and Bradley are a means to get to a place where you can write better Latin not an end in themselves."
Perhaps I am labouring under a misapprehension? Did you write these latin sentences first in Latin and then translate them into English? Well done if you can compose in latin without any act of translation - I am not sure you need my help 
. If however you thought of what you wanted to say in German/English and then produced the latin then I dont understand your reluctance to use readymade sentences that someone has thought about over their teaching career (like North and Hillard) which give practice in the area you want to study.
I dont have Minkova’s book and have only looked at a few pages on Amazon. Unfortunately the classics library I use is closed because of the pandemic so I am not able to look at it nor do I feel like buying it. But I dont see that what she is offering is much different from older writers.
The review I referred you to says:
"The grammatical review is mostly concerned with syntax and excludes accidence, with which users of this book are presumably quite comfortable. The grammar is prescriptive rather than descriptive; Minkova’s aim is clearly to teach the reader how to write correct, classical or rather classicizing (for more on my use of this term see below) Latin prose, without distracting them with diachronic, generic or socio-linguistic variations. The manner and order of presentation are similar to those of traditional composition textbooks like Bradley’s Arnold, but Minkova tends to be more concise. The language is thoroughly up-to-date (Minkova’s English is impeccable and accessible throughout, and readers would never notice that it is not her native language), a boon to those who are not fond of Victorian archaisms. "
I posted the conclusion of the review which ends: “Thus graduate students and professional scholars may find it more useful than undergraduates, but the more motivated of the latter can profit from it as well. This book is also cross-referenced in the Readings and Exercises in Latin Prose Composition by Minkova and Tunberg, which has tons of (fairly challenging) exercises and is its logical complement or continuation.”
So Minkova has published some exercises which might accompany her book. Even following her approach there is no escaping from translation exercise!
I dont want to get involved in a discussion of what’s the best way to learn Latin. The answer to that must be based on your interests and motivation. There are plenty of threads on this forum where these arguments have been aired.
I advise you to take a practical approach. Studying alone you need to make the maximum use of available resources. Try the indirect sentences in North and Hillard or the continuous passages on p 45-47. What is there to lose? Apply Minkova’s explanations to the exercises there. You can also make up your own examples if you fell you need extra practice. Always keep in mind that you end goal is free composition as you work through the exercises!
To return to my musical analogy if you want to play pieces you have to practice studies and scales.
Finally you are not presuming on anyone’s time here! People are always happy to help each other. Thats what the forum is for.
