Hi,
1. I don't see how you can say that custom fields based on shipping methods is something "simple" ?
As I see it, it's quite complex to do it properly. Sure you can do something for your case with a few lines of custom code but to have something which works properly in all the cases, is something else.
2. Sure but it's normal that it works like that.
If you want to skip and go to the next step, then it's possible with some code customization.
3. Isn't that because your browser auto filled some of the login form fields ? What error message do you get ? And please open new thread for new issues with a link to the website, the error messages if any, etc. Adding new questions like that, we have to search for your website URL, read the previous messages, to see if it's there, same for the version number, etc.