Spouse Immigration Petition by U.S. Citizen spouse.

Petitioned for yes, get an immigrant visa, no. I assume that someone is not inside the USA and not just had been ordered deported.

Not very likely, to the point of "No".

Drug felony charge is probably the disqualifier for life and there is no waiver for that.

It would be impossible unless the felony conviction is vacated.

You can petition but based on the limited information you've provided, it does not look like he will be re-entering. You mentioned drug-related felony charges, which is somewhat vague, so it might be better to provide more information so you can get a better and clearer answer.

Maybe. It is likely that the person will still need a waiver. Consult with an attorney as details do matter.