sounds like you need to override the single loop.
dig into the content-extensions.php file of thematic (hint it is in the library/extensions folder). copy the thematic_single_post() function directly to your child's functions.php file.
then you might have noticed something in the content-extensions.php ... basically there is a condition that says if the function childtheme_override_single_post exists that thematic will run this preferentially. this is a rather cool feature Gene and Chris implemented semi-recently. so to take advantage you just rename the function you added to your functions.php to childtheme_override_single_post. you can use this override on almost alllll thematic functions... by replacing the 'thematic' part of the function name with 'childtheme_override'. it is pretty brilliant.
anyway, that gets you
function childtheme_override_single_post() {
thematic_abovepost(); ?>
<div id="post-<?php the_ID();
echo '" ';
if (!(THEMATIC_COMPATIBLE_POST_CLASS)) {
post_class();
echo '>';
} else {
echo 'class="';
thematic_post_class();
echo '">';
}
thematic_postheader(); ?>
<div class="entry-content">
<?php thematic_content(); ?>
<?php wp_link_pages('before=<div class="page-link">' .__('Pages:', 'thematic') . '&after=</div>') ?>
</div><!-- .entry-content -->
<?php thematic_postfooter(); ?>
</div><!-- #post -->
<?php
thematic_belowpost();
}
now within this function you can change the markup/ordering to your heart's content.
it sounds like you will be wanting to take thematic_postfooter and put it in its own div. if you want the postmeta you'll have to override thematic_postheader so that it only shows the title and then probably call the thematic_postheader_postmeta() function in your new div.
it is all in the content-extensions.php file. look in there and copy the parts you want to change to your functions.php