iCloud - HELP!!!!

I know iCloud is meant to be easy but some of us (i.e. me) just don't get it! Can somebody please, in simplistic terms, answer the following questions:

1) When I set up iCloud on my iPhone i used my current Apple ID which is used for iTunes. All fine. When I set iCloud up on my iMac it seemed to prmpt me to set up / fill in a me.com email address. I used to have MobileMe but this expired some time ago. Thinking I therefore HAD to set it up as a me.com account I proceeded to create a new me.com address (as it wouldn't accept my original one). I now have two different ID's (one used when setting up my iOS devices) and one for my iMac. Is this a problem?

2) I now have an iCloud email account which has appeared under my emails App. Should I have this? Is this a result of using a separate MobileMe ID login?

3) When I checked my Calendars App on my iPhone, all of my appointments have been duplicated. I can get round this by deselecting the Calendars on my Mac leaving just the iCloud set. Is this the right thing to do?

4) If any of the above is likely to cause me some issue, can I delete that iCloud account on my iMac and re-set up using my iTunes Apple ID?

Any help gratefully received - whilst I still have some hair left!

Thanks in advance.