I don't think I've ever heard "Kerubim" before. It's the plural of "Cherub", which no one pronounces with a K sound in English. My dictionary says it's a "ch" sound.
I think your classics teacher is getting mixed up with Italian pronunciation (e.g. Cherubini), but Cherub(im) is a Hebrew word.

"Y" is easily heard as an "ee" sound when it's the final letter, e.g. in words like ivy, ready, slowly, etc. At the beginning of a word it generally functions as a consonant.

"R" and "L" are both classified as "liquid" sounds, which can sometimes be almost vowels - or almost omitted - and at other times are very distinct consonants. It's all to do with where they come in the sequence of sounds (and to some extent the accent of the speaker).

Marje