I don’t think -kingur is a suffix in old norse. It is not a suffix in modern Icelandic, and I can’t think of any suffix like that.

In fact I don‘t remember a suffix which attaches to a pronoun. In modern Icelandic at least we like to introduce more pronouns or conjugate them rather then to suffix or prefix them.

If the word was broken as vi-kingur, I think the modern Icelandic would be við-kingur (or við-lingur), which is simply not a word in the language.