Hello the apprentice,
The syllabication rules you listed sound a bit strange to me, and I think the most widely accepted rules (the maximal onset principle with phonotactic constraints) can clear up most of your confusion on this matter.
The maximal onset principle says that any consonants between two syllables should be the first part of the second syllable; in other words, the onset of the second syllable should be maximized. But many experts say that it needs some exceptions in order to make the structures of syllables more phonotactically natural.
For instance, the maximal onset principle divides the word “symbolic” as /sɪ.ˈmbɒ.lɪk/, but no English word starts with /mb/ or ends with /ɒ/, so the second syllable /ˈmbɒ/ can be said to be phonotactically unacceptable. To avoid this inconsistency, we need to put /m/ and /l/ into the first and second syllables respectively. Therefore, /sɪm.ˈbɒl.ɪk/ is the answer.
Then let’s look at “emigrate.” The maximal onset principle (MOP) gives us /ˈɛ.mɪ.greɪt/, but just like /ɒ/, no English word ends with /ɛ/, so it cannot be the end of a stressed syllable. (The same thing applies to /ɪ, ę, ʌ, ʊ/ in a stressed syllable, but note that reduced vowels like /ə/ or /ɪ/ in an unstressed syllable can be the end of a syllable.) And many English words (green, great, groom, and so on) start with /gr/, so it's phonotactically OK. Therefore, we’ve got /ˈɛm.ɪ.greɪt/.
Deceased: MOP → /dɪ.ˈsiːst/ There is no phonotactical inconsistency, so that’s it.
Immigrant: MOP → /ˈɪ.mɪ.grənt/ But a stressed syllable cannot end with /ɪ/. → /ˈɪm.ɪ.grənt/
Couple: MOP → /ˈkʌ.pəl/ But a stressed syllable cannot end with /ʌ/. → /ˈkʌp.əl/
Of course, this syllabication method isn’t perfect, but in most cases, just by following these rules (the maximal onset principle and then the phonotactic principle), you can divide English words into syllables properly.