Your best source for answering your question is the attorney you have hired.
As a general rule, neither party is requried to arbitrate unless there is an arbitration requirement in your CCR. If that is the situtation, the matter must go to arbitration unless both parties give up that right.
Your refernce to a "demand letter" is not clear, i.e. do you mean a letter demanding your roof be repaired or replaced or a demand for arbitration. If it is simply a demand to repair the roof, your lawyer has not committed you to a future course of action. If the letter is demand for arbitration, the letter would be the first step in setting up an arbitration.
I am also not sure what you mean by "committed." If arbitration is required by your documents, the only action the lawyer can take is to bring the matter to an arbitration hearing. The scope of the work the lawyer is performing for you should be identified in your retainer agreement or a letter of confirmation after you initial meeting with the lawyer.
Your last question is incomplete and cannot be answered as it is drafted.
The bottom line is that you need to meet with your lawyer to discuss this matter and make sure you and your lawyer have a common understanding of what you want the lawyer to do for you.
