While all your writing will express your personality, the author bio tends to be the area where authors often feel least comfortable, and can often lead us to become more ‘quirky’ in our writing. This is ok, but do remember that publishers will also want some quite specific information so they can make a commercial decision. This might be about any other work you have published, your professional experience in the field you are writing about, any media experience or exposure you have had, or where you are based.
Writing a synopsis can be hard, so don’t worry if you find this difficult. The key elements you should be expressing are different for fiction and non-fiction, but what you should always be doing is explaining, in a clear way, what your book is about, the narrative arc and key characters (for fiction) or the key areas covered (for non-fiction). Always remember to give away the ending – your editor will, unfortunately, need to know how the story ends. Maintaining the suspense is for the blurb, but never for the synopsis.
In our opinion, as long as the publisher is reputable, this should never be concern. The reason for this is that publishers are in the business of publishing, and are looking for books to publish, rather than to steal. A publisher or editor that did this would always be caught, and would only need to do this once for their career to be over. We would never think that should be a worry. If you do still have a concern, one way to alleviate this might be to email a copy of your work to a relative, friend, or indeed yourself, where the date of the email will serve as a record.