I created a form with text field as I described. I went into Word and created a bullet list with two rows. I copied that and pasted into the default value for the text field. I clicked on the field then the XML Source tab. This is what I see for the value:
<value> <exData maxLength="2000" contentType="text/html"> <body xmlns="http://www.w3.org/1999/xhtml" xmlns:xfa="http://www.xfa.org/schema/xfa-data/1.0/"><p>•<span style="xfa-tab-count:1"> </span>Line 1<br/>•<span style="xfa-tab-count:1"> </span>Line 2<br/><br/><br/></p></body> </exData> </value>
Looks kind of like HTML. Try saving one of the documents as HTML and see what happens if you bind that. You could start with your option 3 except you just need separate text boxes. Write some script to loop through the text boes and save off the rawValue to bind to the final single form. I am assuming the raw value with contain what I see on the XML Source tab.
You probably want you final text box to be auto height and allow page breaks.
I don't know if this will help or not but I've seen talk about getting xhtml into LiveCycle. If you do a search on the forums here you should find a few hits.
Here's a couple of quick links that I found: