Whether or not this particular issue is the cause of the white page syndrome, let's fix it.
Go to your main/home page. View Source (in your browser's View menu). A little more than half way down the page, you'll see where the <html> is.
I assume you put that block of text into the main page using the Define Pages Editor. So now go into admin and open the define_main_page.php in the Define Pages Editor, and remove everything above the text you want -- that is, everything from the <html> down to and including the <body> tags. Then scroll down and remove the closing tags for body and html too. Save. Now your main page is fixed.
The other problem -- the missing text -- is usually caused by something like a missing end tag in the PHP somewhere, or missing quotes in define statements (also in the php). And these can be caused by extraneous tags inserted while editing things like product descriptions. Not that tags go missing when you do that, but tags added when you do that can cause the browser to become confused. So if you've used Dreamweaver to create the text you insert into product descriptions, then you may have to go through all of them to weed out the problem code.
What I'd suggest is that you find a page where the problem can reliably be replicated, and check that exact page in the w3.org validator. Then read through its response and try to figure where the problem is coming from. You can ignore warnings, just concentrate on the errors.
Rob
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