I'm not a lawyer...although I'm well versed in this area...basically your contract is an ok unsigned artist contract....Definately do this:
5. RELEASE OF RIGHTS: Producer will release all copyrights of master instrumental to Artist in exchanged for a one time payment (to be negotiated at time release of rights) of not less than One Thousand Dollars ($1000.00) and not more than Ten Thousand Dollars ($10,000.00) and guaranteed co-production credit on any release of the master instrumental. Producer will receive zero royalties.
Take out the last portion so the statement reads like this
5. RELEASE OF RIGHTS: Producer will release all copyrights of master instrumental to Artist in exchanged for a one time payment to be negotiated at time release of rights.
That artist could sign a major deal with the efforts of your music and recording so don't give away anything for peanuts....You'll negotiate the price at that time...Don't put a cap their and don't say you won't recieve any royalties....Let the situation dictate what the fair price is....the sentence doesn't need to be their and it can only hurt you--so my advice is take it out.....
I would add that if the artist does sign a major recording contract do to the efforts of your work...you reserve the right to the production of at least 1 of their songs off their first album....