This is the best I can do quickly. Of course, the Italian words communicate far more than a simple literal translation can do.
"I had nothing better to do" is a correct translation but in the context of the song there is a melancholic tone to the words that the translation cannot really convey.
The passage"Ed ora / che avrei mille cose da fare" once again doesn't quite convey the meaning as well.

The translation to "And now / although I should be doing a thousand other things" is correct but in English I would more likely to say "And now I should have better things to do" but I decided to translate it more literally to help those learning the language trying to give a more 1:1 translation rather than a more colloquial or poetic one. Enjoy. Tenco was a genius and an incredibly talented guy. His influence has transcended the few years he was alive. We can only regret how many more songs he could have produced. Then again, he was crystallized like a fly in ember and that's part of his charisma. He could have gone totally commercial in the 70 like many others did. But he could also have followed in De Andre` steps and given us so much more.