travel document number is a number needed if a person was traveling without a passport/visa. so when I was self filing my forms I put (N/A) not applicable.

all my forms were excepted with no rfe.
it's always nice having a lawyer to go through and fill out all those forms. but if you can't afford one do a lot of research and also there are tutorial videos on exactly how to fill out the forms. more importantly read the instruction pages for each form it tells you what to put for each question.