This email address is not available for use as an Apple ID

Thanks for asking the question. I had a similar situation and I have solved it in my own case. I had a duplicate/s accounts one of which referred to my gmail account. My main ID for apple had apps associated with it and apple orders so wanted to continue using, but it was an old ID so not yet converted to be an email address which caused problems when trying to setup an icloud account, so i needed to change my main ID to be my email account and obviously wanted to use my main email account, but this you guessed it tied up with one of the duplicates. Tried changing ID in duplicates and removing secondary email addresses but did not seem to 'free up' the email address. Was going to use a completely different email address and then remembered that you can use @googlemail.com and @gmail.com interchangeably for gmail accounts. So I have set my apple id to the googlemail one. Hope this helps someone too.

Thanks, Will