Horrible beginning

My assignment:
Querido Dr. Peterson:
Es un verdadero honor para nosotros que haya contestado a nuestra carta.
Agradecemos enormemente sus observaciones y entendemos que en nuestra carta, por no extendernos demasiado, no nos hemos explicado con suficiente claridad.
Si le parece bien le contestaremos a sus observaciones una a una:

and my attempt:
Dear Dr. Peterson,
it is a truly honor for us that you have answered to our letter.
We greatly appreciate your observations and we understand that in our letter we have not explained clearly enough, because we only present main ideas.
Considering your observations, we will answer to them one by one:


I don't know why but it sounds horrible to me. Please, help.

No. The translation is bad and the whole reply is overly formal. So let's make another try:
Dear Dr. Peterson,
we are happy that you answered to our letter and really appreciate your analysis. In order to clarify a little more herein we answer to your considerations one by one:

Thank you.