As a coder, your job is to code accurately based on the physician's indications and orders, not to code only that which will get paid. You can educate them later about screening vs. diagnostic, but don't compromise your ethics by coding only for payment.
Based on what documentation that you've shared, is the patient currently using ETOH? Then code alcohol abuse. If they're in remission, code it that way. A screening is only appropriate if there are no symptoms that the doctor provided as an indication for the EGD.
Best answer I could give you today is to not look for coverage guidance here on the forums. Everyone's an expert, but unless they provide specific regulatory guidance, you're getting nothing but an opinion. Check Medicare and the commercial payers for their coverage indications for EGDs.
https://www.cms.gov/medicare-coverage-database/view/lcd.aspx?lcdId=33583&ver=21