Client disowning his commitment towards work undertaken

Hello, we are a startup research and consulting firm based in Delhi. We started working with this client in /October/November 2014 to support him with his product launch (Logo Designs, Packaging, Corp Identity, Research and Website) all under one project. In the middle he abruptly asked us to stop research and the website was not initiated as per discussion , this client asked us to adjust the amount later and based on calculation a sum amount was decided which was agreed to be settled against the final delivery. He cam back said all the products he decided to launch are put on hold there is another category which he wants to launch for which we clearly stated will be a separate project and separate billing, as we come close to the delivery he is staring to go against the agreed terms and is asking us to settle the amount for the previous work , and the balance to be paid . we are agreeing to the same and want him to sign a document which clearly states timelines of delivery of both the project and if there is a delay by either parties either on approvals or delivering the job there will be penalty charges to safeguard the interest , the client started using abusive and un-parliamentary over email and calls and keeps on threatening us to press fraud charges which are baseless as we have all his emails accepting to his terms but he is trying to get work done for either free by extracting the money back or spoil our image. We have tried ways to help solve this but he is trying his ways to pressure us down thinking we are a startup. I request you to help advice how can we tackle this and the required steps.