1) You can set css sytle for .form-conrol.input-sm, add this text to the multi choice question:
Code:
<style media="screen" type="text/css">.form-control.input-sm {
width: 800px;}
</style>
2) You can use group by group mode. Add new question in the same group where multi choice is. For example, multi choice is Q1, long free text is Q2. Add option to the Q1 with something like "I'l type my answer", for example that option is Q1_SQ004.
a) Set SQ004 as Exclusive option in Q1 to block other checkboxes.
b) Go to conditions page of Q2.
c) Select Q1:SQ004 and Checked then press Add condition. You will see somethink like "Q1:SQ004: [I'l type my answer][Single checkbox] Some text (qid1216)"
d) instead of b and c you can open Q2 and type (!is_empty(Q1_SQ004.NAOK)) in Relevance equation field.