difference between e and é?
so I know what's the difference when it's at the end, but when it's at the beginning or in the middle of the word, how do those differ?
By their sound. That's the role of the acute accent in French: to change the sound of the letter "e".
It's common to not ear the difference when not used to, with time your ears will get used to the difference: they are really different sounds for native ears (and for ears (sufficiently) exposed to them).
I've also had a similar problem with those spellings. I think e is used for reduced vowels (/ə/) like in reposer (or, of course, for other spellings combinations like eu, eux, eau etc), while é is used when you need to pronunce clear /e/ like in répondre. The é is also used in words where some other rule tells us to pronounce it like /e/, eg. manger, voulez. So there isn't really any other mysterious "slight difference" between these sounds. Am I right or is there something I haven't noticed?
Yes, you are right, but there are cases where the "e" is pronounced like a clear /e/ but doesn't have an acute accent :
- When the "e" is followed by "d", "f", "r" or "z" or is at the end of the word (pied, nez, etc.)
- When the "e" is before a doubled consonant (effet, essai, etc.)