lease purchase question

Hello anyone. I live in michigan and have a question about a lease purchase. My girfriend and I did a lease purchase on a home and it is to be purhased next year. Our lease is written up on a purchase agreement sheet drafted up by a realtor. Our landlord called tonight and said that we need to finance the house now and the rent is going up from 1100 to 1700. He has been pressuring us to buy it since day one. The contract that we have has just the date of purchase, the payment per month and that the seller pays taxes for 05,06,07 summer and winter taxes. He got irate with me about the payment when I questioned the rise in rent. The contract has the rent could raise or lwer this year from the interest rate but he is telling me his taxes went up so that is why the rent is going up. I do not know alot about contracts but are there problems with this contract on his part because I don't understand how he can raise rent 600 dollars and keep forcing us to buy now. Was ther supposed to be a lease agreement also and with all of this can I break this lease so I can find a new house because he is trying to rip me off. Please if anyone can help it would be greatly appreciated.