My 301 threads from right to left as well.
I couldn't really tell because the picture is too small, but i believe you are missing a guide. To the left of the spool and just behind the front guide. It would attach to the back of the machine. I think you will find a small hole on the back left of the machine at the top. I bought a set of guides on Ebay for a total of $9. Check out some pictures on the Singer site to see it. DO you have the book? you can d/l that free from Singer.