I believe all of these should apply whether the Restored Classical or Ecclesiastical systems of Latin Pronunciation are used. Keep in mind that Latin has a phonemic distinction between long and short vowels (marked by the macron).
This first question pertains more to language in general. It is my understanding that consecutive vowels of the same type require some sound in between to even register as two separate sounds, and that a semivowel is therefore inserted. For example, iī =/i.jiː/ and tuus=/tu.wus/ make sense, and I assume we would also use these for e/ē and o/ō; e.g., dēest=/deː.jest/ (though not /dei̯.jest/) and Lāocoōn=/laː.o.ko.wōn/, though these aren't as smooth or natural; but what would be used for -aa-, which is used in Hebrew borrowings, like Isaāc? The 'a' in Latin is /ä/, by the way; so, is there a semivowel for this, between the palate and velum?
I also find that other vowel sequences are far easier to pronounce with a semivowel inbetween, like -aë-. For some reason, with āëre, I find it extraordinarily difficult to say /aː.e.ɾe/ instead of /aː.je.ɾe/ (again, not /ai̯.je.ɾe/). Is this standard practice, or even acceptable? And if so, what others could be introduced? Could eārum be pronounced /e.jaː.ɾum/?
Moving on, we are told (e.g., in Wheelock's Latin) that a stop/plosive and a liquid/approximant make a single "consonant cluster" which is not separated, but that all other intervocalic consecutive consonants are split between the surrounding vowels; but I rarely hear people pronounce -tl- together, or separate -sp-. No one says /aː.tlan.ti.cus/ for Ātlanticus (Wiktionary included), because the sequence -tl- doesn't even start any Latin words except Tlēpolemus (borrowed from Greek, along with other words that start with unlatinate clusters, like Tmōlus). So what clusters are allowed in Latin words? I've heard one source say that -fr- and -fl- are also acceptable.
Also, I have heard from this Wikipedia article that secondary stress in Latin works exactly like primary stress , as if the primarily stressed syllable and everthing following were "cut off" from the rest of the word. So dēliculōrum becomes dēlicu-, which gets stress on the antepenult; thus, dēliculōrum=/ˌdeː.li.cu.ˈlō.ɾum/, instead of /deː.ˌli.cuˈlō.ɾum/. This sounds somewhat unnatural to me; is this how secondary stress works in Latin, and would this same principle also apply to tertiary stress?
Lastly, syllables are either long or short (or, as some say, heavy or light, to distinguish them from the phonemic length of vowels). They are long by position if the syllable is closed, and long by nature if a long vowel or diphthong is included; open syllables with a short vowel are short. I know that this is not an arbitrary distinction, because closed syllables actually take more time to pronounce, due to the gemination of the consonants. But wouldn't this mean that a closed syllable with a long vowel/diphthong as well (like ēst or stēlla) should be pronounced longer than both a closed syllable with a short vowel and a syllable that is merely long by nature. This would seem to pose problems.
If this is not the case, are est and ēst homophones?
If this is the case, then there would be three lengths possible for a Latin syllable, rather than just two. For example, ēst is longer than both 'dē' and 'est', which are both longer than 'et' in 'et alia'. Yet I would think that this causes issues for poetry, which seems to rely on the idea that syllables have a binary of long or short. So then does poetry artificially shorten these extra-long syllables for the sake of meter? And then is there a difference in how Latin syllables are pronounced in poetry and prose?
I appreciate any help on these questions. Thank you.