For PayPal hosted overriding the item_number, I haven't been able to find a good PHP example overriding a PayPal hosted button. If you know where I can find a good PHP code example overriding a PayPal hosted butto, please let me know. I have looked before posting.
Paypal buttons are just an HTML form with a bunch of hidden inputs set up. In PHP it's as simple as something like this:
<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="hosted_button_id" value="YOURBUTTONID">
<input type="hidden" name="item_name" value="<?php echo $itemname; ?>">
<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
Unless I'm misunderstanding the question.
Also as an FYI, the item_name field is solely for your use and not something Paypal cares about so this may be unnecessary unless you need it for internal reporting.
For dynamic encrypted buttons, I found a site Stellar Web Solutions on how to create PayPal encrypted buttons using openSS stellarwebsolutions.com/en/articles/paypal.php. Since I'm on a shared server, I don't have command line access. They also have a Wizard to create a certificate. Is this a well known, safe site?
Get off your shared server if at all possible. Virtual private servers cost as little as $5/month nowadays and you can run whatever you want on one.
Also, for IPN do I need an SSL?
Not in order to receive IPN notifications, but I recommend SSL for lots of other reasons (privacy, etc) if you can afford it.