White page after deprecated function

Worked just fine for 4 years and yesterday started the nightmare.
To do it short : I had to fix the wpdb::escape() deprecated function__ok so I had an other error : get_current_site name, fixed too. And when I thought everything was ok, guess what ?
My main site is a white page
My 3 others sites just display home page, all the other pages display 404 error…
What to say, haunted forums all night, (I have to deliver a site in less than 10 days), harassed my FAI that sent me back to wp forums and for now still looking for a solution, I feel depited and desperate ! Any fix ?