That is because in that part, the word theos has no article. So it can be translated "a god". And it is not very clear in John 1 that the Word (Logos) is Jesus himself. Some denominations say it is the plan of salvation. That could make a lot of sense.
Then you say the world was made by him, but the preposition in Greek is dia, meaning normally 'through'. So it could be translated in verse 3 "through him" or "through it". But we are not supposed to know if the Logos is Jesus or the plan of salvation, that is why it is ambiguous in John 1. But I think when Jesus comes back, he will explain to us all the difficult Bible passages, and we will know.