Well I found out that all but one of the validation problems was caused by the translation to WP from Textpattern. Not txp's fault, but mine.
HOWEVER: there remains a problem in the search form: it uses an odd html form element in the general-template.php file:
$form = '<form role="search" method="get" id="searchform" action="' . get_option('home') . '/" >
This causes the validation error:
Attribute "role" is not a valid attribute. Did you mean "frameborder" or "scrolling"?
…s="widget widget_search"><form role="search" method="get" id="searchform" act
So we're at the mercy of WP to upgrade, or simply hacking the core file ourselves.
One upscale tidbit: I fixed the broken article from txp by simply editing the article doing nothing (insert space, then delete it), then saving it in the WYSIWYG editor. It looks at the html and fixes problems like improperly balanced tags! Way cool.