Some partnership! Obviously your partner isn't serious about the deal or you wouldn't have been delayed. That is unless you made up the deadlilnes yourself. Have you seen the work? If not, just say to him, "have a nice life", and move on with absolutely no obligation.

If you have seen the work and you want to use it knowing you will need to pay for it, you need to negotiate the best deal for you. I'd bet that as soon as your partner knows there's money in it it will soon become the most important project ever! I'd offer a very low 100% all rights and files buyout.

Hope this helps.

Kent Capener
Capener Consulting, LLC
http://www.capenerconsulting.com