Marketpress Issues (WSOD)

Marketpress Lite worked beautifully, even with my custom theme. This is what prompted me to purchase the full version... Especially since all other e-commerce plugins broke my site. However, upon installing the plugin, my admin backend breaks (WSOD) and can only be recovered by deleting the plugin via FTP. I've installed via FTP, but upon activation, dreaded white screen.

WP 3.5
PHP 5.3.18 (Maybe a php updated needed?)
Shared hosting (actually, SHARED, shared hosting... Multiple sites on host, separate domains)
Custom Theme (Photo Album by H&H Color Lab)
No other plugins activated.
WP_Debug; true

Notice: add_custom_image_header is deprecated since version 3.4! Use add_theme_support( 'custom-header', $args ) instead. in .../wp-includes/functions.php on line 2824

Notice: add_custom_background is deprecated since version 3.4! Use add_theme_support( 'custom-background', $args ) instead. in .../wp-includes/functions.php on line 2824

Notice: get_theme_data is deprecated since version 3.4! Use wp_get_theme() instead. in .../wp-includes/functions.php on line 2824

Warning: Cannot modify header information - headers already sent by (output started at .../wp-includes/functions.php:2824) in .../wp-includes/pluggable.php on line 876

Warning: Cannot modify header information - headers already sent by (output started at .../wp-includes/functions.php:2824) in .../wp-includes/pluggable.php on line 876

If I use the standard 2011 or 2012 themes, I get a memory error. *(I have not attempted to correct this issue yet, as Marketpress Lite worked just fine - although I'm sure the full version is a bit more demanding)

Any insight on this issue would be welcome. Coding noob here, so I'd need a helping hand if it comes to major revamps of code.