Just a quick subjective question… In the earlier days of memorisation, nouns seemed so much easier, but now when I hear or read a phrase or short sentence, it is the verbs that stick in my memory more clearly.
I haven’t read about this in the SLA literature.
Does anybody else have a similar experience with their Greek?
No, I haven’t noticed any distinction between nouns and verbs in terms of retention.
The only way I’ve discovered to make vocabulary permanent is to meditate on a text for a considerable period of time. The vocabulary I encountered reading through a text for the first time is shockingly impermanent. One way to improve retention is to take copious hand written notations which I routinely do with difficult material. Writing the words down with lexical semantic analysis also helps somewhat, however it is no guarantee that a month later I will know that vocabulary. Meditating on a text for prolonged period of time is very effective.
I would say at the current level of my Greek there is no real difference in the internalization level of nouns versus verbs. Probably at earlier levels nouns were easier to memorize/internalize, possibly because nouns tend to be more concrete in meaning and a little simpler in form. Mounce, as you may know, teaches nouns first. On the other hand, Rico and Buth, influenced by Total Physical Response learning strategies, introduce stuff like στῆθι and κάθισον at the earliest level. I think my own kids used more nouns than verbs at the earliest levels of speech.
If there is one thing we know about SLA, it is that different people learn differently, so I suspect some will share your experience and some won’t.
That is similar to another difference that I have noticed. There has been a progressive change from remembering sequences of sounds to memorisation based on understood language.
Similar to your writing and re-writing, I found that repeatedly going over the sequence of sounds in my mind is a good to (eventually) attach meaning to the sounds.
The situation is quite different if I understand what I am reading it. In that case, I tend to remember those parts of the phrases that I understand in a different way. For example, after reading this passage
a few times today, I was able to reproduce it as:
Presumably, the literary technique of talking about oneself in the third person, the dative singular of sillibant stem of first declension nouns and adjectives after a repeated article, are three things that are either not actively used in my interlect (or at least not prototypical in it). My mis-remembering those things perhaps suggests that those are points of the language that I need to practice more. I think that even a short mis-remembered phrase is a good starting point for correction and for eventually building it up into the perfect original.
Except in the case of cognates that I hadn’t realised at first glance, my first and second pass vocabulary is a sieve which wide gauze - only the most weighty things remain.
Let me ask a few things about where you are at:
I guess that beginners would treat those commands as single functional units of the language, rather than a grammaticised root.
The Colloquia of the Heremeneumata Pseudodositheana introduced beginning learners of the language(s) to all sorts of useful phrases and expressions, with the kind of simplicity one tends to encounter in daily communication, but not shying away from forms that might be considered “difficult” for beginning students today, such as hortatory subjunctives or indirect discourse using the accusative and infinitive.
I haven’t tried to memorize vocabulary since I finished my 1,000 Vis-ed ancient Greek cards decades ago (or the equivalent set of biblical Hebrew cards a little later). My vocabulary acquisition is simply through reading and re-reading texts. But I try not to read them too many times, lest Michael accuse me of fanaticism… 
Also of interest:
https://theconversation.com/youre-never-too-old-to-become-fluent-in-a-foreign-language-96293
When I encounter new vocabulary I try to learn it, by relating it to vocabulary that I do know, and in context.
With certain exceptions I would rather read a new text than one I’ve read 500 times or even twice before. On the subject of everyday communication, does anyone except prep school latin or greek teachers still use “lest”?
Dictionary.com lists 3 examples from articles found on the web published in 2014. What do you want to bet that the authors all took Latin at some point?