Real State Cancellation and Refund

We just want to ask for your legal advice regarding our case. We bought a House and Lot in Laguna last 2008. It was in installment basis payable in 10 years. Now, we cant afford to pay anymore because a large part of our monthly pay goes to the interest and penalty that they are charging to us. that until now, the principal contract price is not even changing, so we decided to cancel the contract. When we went to their office last August 18, 2012. We found out that they sent us a notice last May 2012 (which we didn't received) saying that our payment and contract are already forfeited since January of 2012.This are my questions.

1.) We are still paying them from February to April of 2012 but the contract as the notice says was already forfeited last January 2012. Can we refund the payment made last February to April 2012?
2.) We found out that the "Contract to Sell" was not signed by us and the developer. does it mean we can refund the whole amount that we paid to them?

3.) They are saying that base on the computation we have an arrears on the interest and penalty. that if we will cancel it we will not get anything and we have to pay them for the arrears. is this correct?

I do know some from RA 6552 ( Maceda law) saying that i can refund atleast 50% of all the payment we had but they are saying we will not get anything. What shall we do on this?

Kung interested ka parin sa property pwede kang mag request sa developer ng restructure of payment para di interest at penalty napupuntahan lahat ng payment mo