Hi John,
I think that his real name may read Kitagawa Katsuichi.
As for the second question, it is very difficult to answer, because I unconsciously read them in most cases.
I am thinking of my reading procedure again;
Regarding 北川 for an example, I might have judged the kanji as a family name before actually read it with sound. Because I was reading a mei on a nakago and I knew that 勝則 must be a smith name from my experiences, 北川 was naturally thought to be a family name or place name in most cases. However, 北川 is common as a family name, while it is rather miner name as a place to be used on a mei.
If it was a family name, its usual reading was Kitagawa or Kitakawa. Hokukawa or Hokkawa could be its reading, but I never thought of that, because its possibility is small (but not zero) as a family name.
Generally, the readings of proper nouns in kanji are difficult except you know their names beforehand in your memory.