The deprecated notice is pretty clear:
Usage of user levels by plugins and themes is deprecated. Use roles
and capabilities instead.
The only place you use a user level it here:
add_options_page(
'Seach by Category Options',
'Search by Category',
10,
basename(__FILE__),
array('SBC_Admin', 'config_page')
);
See that “10”? Don’t do that. Use a role, such as “administrator”, or a capability instead, just like the message states.