TEFL to native Spanish-speakers

Does anyone know where online I might be able to find a list of English words that native Spanish-speakers typically find difficult to pronounce? I´m teaching intermediate and advanced English conversation classes in Ecuador, and pronunciation is one of my students´ biggest concerns. I do of course correct them as we go, but I´d like to do a lesson specifically on commonly mispronounced words.

Alternatively, where might I be able to find a paragraph or page of English that includes many difficult-to-pronounce words?

Finally, can anyone suggest some vocabulary sets that would be appropriate for the intermediate level? In my mind, greetings, seasons, colors, numbers, clothing, family vocab, etc. are all basic topics... what might be good for intermediate? What about grammar topics? (My students have requested irregular verbs and indirect questions.)

Thanks so much!

ETA: Also, what might fellow TEFL teachers recommend I do given that I am completely unable to understand some of my students´ written work? I´d correct it, if only I knew what they were trying to say...