You can have several Apple IDs - you would need to have a different functioning address to act as the ID in each case but that's not difficult.
The ID for iTunes doesn't have to be the same as that for iCloud - iTunes purchases, iTunes Match and 'iTunes in the Cloud' are actually not related to iCloud in any way.
Also you can easily run two iCloud accounts simultaneously on one Mac; one would be the 'primary account'; the second would be signed in in System Preferences>Mail, Contacts and Calendars; synced data would appear alongside the primary account. Only the primary account can access PhotoStream and Find My... , and the secondary account doesn't get 'push' email but checks the mail at intervals.
You could add a third account in the same way, but note that any one device can create only three iCloud accounts. This is tied to the hardware, not the account, and once you've reached the limit that device can never again create an iCloud account by any means (though it can sign into another account which has been created on another Mac or device).
Can I switch my iTunes, documents, iMovie progjects, etc. from my current iCloud/Apple I.D. over to a new I.D. and iCloud account - basically just wanting to change my Apple I.D. and get new iCloud address, but have way too much to lose while transfering over to new accounts.
Maybe even keep everything as is (file-wise), but changing account info? I'm not sure how to relate. Seems like I could download all itunes to this MacBook, back everything up, creat new i.d. and iCloud, upload everything to new account/s.
Is this considered sharing?
I am trying to get new iPhone and, soon, an iPad so I am wanting a new "fresh-start" to everything or rather give it all a new feel - PLUS spam e-mails and third party haters are too frequent with mail and feel like new address would help some.
Hope I'm not making it all more complicated than it should be.
You can't move purchased iTunes items from one account to another. iWork documents can be uploaded to a different iCloud account. Other types of documents and files don't come into it because there is no general file storage on iCloud.
You would be best advised to leave the iTunes login alone but start a different iCloud account and manually transfer any related documents and data. There's no problem about their being different accounts, and the spam problem has no effect on iTunes; however I'm not sure about the contact address issue with iTunes - it may be stuck with your ID: you could ask in the iTunes forum about that.