Kudos to your first english attempt. Back then, most people did very disorganized CVs. I won't be a VCCV™ preacher who insists on it being the One True Reclist, so of course I'll leave feedback instead.
It's better to represent sounds using more phonetic notation than terms like "short and long vowels". English no longer has short and long vowels in the general linguistic sense because of the changes that occurred during the Great Vowel Shift. Therefore, referring them to as such would only make sense to those raised in english-speaking schools where the present day vowels are taught as being in said groups. This makes the reclist unsuitable for nonnative speakers.
Standard worldwide language notation is called the International Phonetic Alphabet, or IPA. Because UTAU is unable to support unicode symbols, we have to circumvent this by inventing our own systems of representing sounds. This is not necessary. X-SAMPA already exists and directly corresponds to every symbol in the IPA. Vocalsynths such as Vocaloid and Chipspeech/AlterEgo, both developed by professional music companies, use this notation already.
Reclists are, essentially, a list of all possible syllables in a language. In order to make a list, you need the phonology, or the sounds and what they do, and importantly the phonotactics, or the rules for syllables. English has many clusters and diphthongs, and it seems that you are attempting to avoid these by removing them from the reclist, then relying on end-users to piece together dozens of tiny little notes in a UST just to make one word, like "twelfths" or "strengths". Additionally, you seem to be missing some sounds.
This is the wikipedia article on English phonology.
https://en.wikipedia.org/wiki/English_phonology
It might seem scary and full of complicated linguistics terms! But as a reclister, it's your responsibility to decipher what all of this means into a simpler form that an UTAUser can take away as a useful resource.
There's also the matter of your reclist's organization. It's much more efficient to have a sas sample than to have separate sa and as samples, unless it's a language in which the CV and VC components are regarded as very separate entities. Also, you suggested recording sa and sA into the same file together without actually listing it that way in the reclist. When you distribute the reclist, you should compile all the samples into a text file with the samples being exactly as the file names should be. Reclists should be made to be OREMO compatible, even if you don't personally use them that way.
Anyway, I already have a reclist that achieves the goal of being a simple basic English reclist for those who don't want to record or oto much. No shame in the overlaps, because it's great to practice writing reclists. It gives you a better understanding of how to use UTAU. But I personally believe that it's better to write reclists for the sake of yourself than for the sake of the UTAU world and hoping that you get noticed, and start a reclist cult. (In fact, LEXYS was written for my 7 year old sister!)