broken database when trying to set up multisite from existing WP site

Yikes!
I added define( 'WP_ALLOW_MULTISITE', true );
right before /* That's all, stop editing! Happy blogging. */

Then I replaced the WordPress rules in .htaccess

That resulted in a 'broken database' message with instructions to insert a repair code in wp-config.php which I did just above /* That's all, stop editing! Happy blogging. */

Now I've got an eternally long error list:
wp_5u5a9t_1_posts: Table 'cobbles8_wp.wp_5u5a9t_1_posts' doesn't exist
wp_5u5a9t_1_comments: Table 'cobbles8_wp.wp_5u5a9t_1_comments' doesn't exist
wp_5u5a9t_1_links: Table 'cobbles8_wp.wp_5u5a9t_1_links' doesn't exist
wp_5u5a9t_1_options: Table 'cobbles8_wp.wp_5u5a9t_1_options' doesn't exist
wp_5u5a9t_1_postmeta: Table 'cobbles8_wp.wp_5u5a9t_1_postmeta' doesn't exist
wp_5u5a9t_1_terms: Table 'cobbles8_wp.wp_5u5a9t_1_terms' doesn't exist
wp_5u5a9t_1_term_taxonomy: Table 'cobbles8_wp.wp_5u5a9t_1_term_taxonomy' doesn't exist
wp_5u5a9t_1_term_relationships: Table 'cobbles8_wp.wp_5u5a9t_1_term_relationships' doesn't exist
wp_5u5a9t_1_commentmeta: Table 'cobbles8_wp.wp_5u5a9t_1_commentmeta' doesn't exist

and a nonfunctional website.
HELP!!! I'm really drowning in this!