In the page “Conversation with Carina Molier” once you click on a post, there are a couple of things at the end of the post page “About the author” and “About the post” Is it possible to remove these?
remove about the author and or post can be removes depending on the theme, html & css code can sometimes help.
In the contact page, I wanted to place directly my email address and phone number, but I am not sure what is the safe way to do that to avoid spam. Could you give me your advise?
Stating your mobilephone in plain text is a safe way to communicate it.
Spam is almost always finding its way through the comments of your post or a contact form.
If I need to buy the premium account in order to have control over these things, then how much is that? And does it include having a custom url address – without wordpress mentioned, and without reference to the theme name in the footer? And if I buy a premium account, will this remain valid if I change the theme later?
A better way to go premium is to register a personal domain [example] and install the free version of wordpress.org. This free version gives you all the features and flexibility to completely design your blog / website to your liking, easily, including all the premium themes.
references in the footer can be switched of with a mouse click this way