Chapter 13 and then a foreclosure in Massachusetts?

I have been in a Chapter 13 repayment plan for the last year. Due to my adjustable rate mortgage, my payment has gone up. At the beginning of the plan I did not sign a reaffirmations on my mortgage, but I have continually paid my mortgage payment on top of my Chapter 13 repayment plan and now with my mortgage payment going up, I can not afford to pay the mortgage. I think it would be best for me to let the house get foreclosed on, but I want to continue making the Chapter 13 payment.

Question 1: If the house sells for less than what is owed, am I still responsible for the deficiency?

Question 2: Will I still be able to make my Chapter 13 repayment plan at the same amount that I'm paying now?

Question 3: Will I still get my full tax return refund?

Question 4: Does anyone know if Massachusetts has a foreclosure deficiency law while I'm in a Chapter 13.

Any advice would be helpful!

Thank you.