to remove the width issues for the button:
1.) line -1137 --> remove $baseline*2 rule for .discussion-article
2.) change line 1400 to padding: $baseline*2 $baseline*2 $baseline/2 $baseline*2; (this adds back padding to the .discussion-post
3.) change line 1446 to have padding: 0px $baseline*2; (adds padding back to reponse OL)
4.) change padding rule for .discussion-reply-new to padding: 0px 30px; 
5.) This will let you remove many of the padding and margin rules, as well as the width:102% for the add a response button.