it's "e l'amico" not "ed l'amico". yes, if the next word starts with "e-" you can use the conjunction "ed". Peachey's example is correct. It's less common using it before words starting with other vowels like: "tu ed io"/ "tu e io" ciao.

YES. PS. There's an L in your example. Perhaps you meant something like "Tu, ed Elmo"?

Yes, but in your example there's an "l" so you have to write "e l'amico". It's the same with the "a". For example: "Lui è andato ad aprire la macchina". You put a "d" because the verb "aprire" start with a vowel.