J. J. Kneen's English-Manx pronouncing dictionary gives the pronunciation kel, where the k and the e have the same value as in English (short e), and the l has a subtlety that does not go to your query, which is about the vowel sound. That does not help with your conjectures, for the pronunciations you list all have a long vowel sound, where as keyll, according to Kneen, has a short one.