Got the White Page of Death

I really need your help! It is 3 am in Texas and I have been trying to fix my goof up for two hours. I changed themes on my blog at https://internetmarketingreview.org/blog and got a blank screen afterwards. Even the admin. panel is gone. I went into my FTP and deleted the theme I had installed but still, I can’t get my blog back. I backed up my files. I called Yahoo, my host, and they said it was something they couldn’t fix, I would have to ask for your help.

Please tell me what to do. I need to post some work today that I will get paid for.

Thanks in advance.