I'm glad someone else took a chance at attempting to help your predicament, and there probably isn't any better advice.
Really, the whole vowel system in phonetics is abstract. With modern imaging techniques, the whole 'vowel space' that Daniel Jones introduced with close, mid, open/front, central, back distinctions, we see that these distinctions are just too inaccurate.
The best way to learn vowel sounds is probably by listening and imitating. No amount of description would work - the movements are just too intricate and complicated, especially in connected speech.
Also, vowels are one of the main distinguishing factors in different accents, and there are many different accents in native English speaking countries, as well as many people with English as a second language who bring their own accent to the language.
What I mean is people are very forgiving of accents, and thus of vowel idiosyncracies. It might cause some amusement. For example, in my own accent, I pronounce 'ice' the way many English speakers pronounce 'ace', and the way I pronounce words with an /aʊ/ diphthong in RP English causes great amusement for my fiancée, who speaks English with a Brazilian accent and says /aʊ/, in a sentence like 'how now brown cow'. Apart from amusement, it shouldn't cause too much bother.
