All I want to do is use icloud.com as my primary email address and ultimately get rid of gmail. Apple are preventing from doing that, which seems crazy to me. I have already set up gmail to be forwarded to icloud, but that was supposed to be pro tem for say 6 months. Now i will not be able to sever gmail, unless I create another non-Apple email address!! As I said before, what is going on!
When you start from scratch you can create an @icloud.com address and use it as your ID, but though it seems illogical you can't do what you ask. I don't know whether this is a technical issue.
However, I would suggest that having your published email address as your login is poor security. This used to be the case with MobileMe and there were quite a number of complaints from people who had found themselves locked out of their account because some idiot had tried to sign into their account several times without knowing the password. They then had to change the password in the ID and all their devices, and a couple of weeks later it would happen again.
This sort of nonsense sometimes arose through mis-typing, and sometimes because some idiot would become convinced that he owned the address and would keep trying to log in with it.
Of course, someone who knew your email address and felt malicious could render your account useless by keeping on doing this. I know all this sounds a bit extreme, and it is moderately unlikely, but these things do happen.
For best security, I would suggest creating a new free address somewhere with a garbage username which can't be guessed and is unlikely to be arrived at by accident. I know it's less convenient that logging in with your @icloud.com address, but you might like to think about the security issue here.
iCloud mail is as secure as any other service. What I'm saying is that using your @icloud.com address as your login is poor security. If someone knows your address but your login is different, then they can only send you emails. But if your login is the same as the email address you give out, then they know your login. Of course someone who makes a mistake or is an idiot could just as easily cause the same problems with your existing login address (which is why I suggested some complex garbage as the username for it) but giving people an address to try is just adding to the issue.
All this is isn't a high security risk, it's just that we did have a number of people with that problem in the MobileMe days. But in any case it's academic for you as you can't use your @icloud.com address as the ID even if you wanted to. I was just suggesting that perhaps that wasn't a bad thing.