Both properties are run-down and have long-term tenants who do whatever they want (unauthorized pets, subletting, building unauthorized structure, smoking, etc).

Days after the inspection, the buyer and his agent came by the house (based on notification from the keybox), and did their own walk through and responded back saying that the smoke detectors were not working and the electrical panel needs major work. 

They also require a roof, chimney and furnace inspection which my inspector told me all were in great condition.Other things needed are fire extinguisher and an additional smoke and co detector.

It's also acceptable to hold tenants accountable for consumables like light bulbs, smoke detector batteries, or filters in the refrigerator.

Can't cook food = not a kitchen = not a house, in Fannie Mae's eyes.Example of a go: 1970s gross yellow wallpaper stained with cigarette smoke, fridge from the 1980s in that yellow color. 

How many people living with you smoke?

Start smoking cigars.

for example smoking in the apartment or being loud past a reasonable hour.If an occupant who isn't on the lease is involved in domestic violence against my tenant, will I have the ability to evict them from the property even if the tenant wants them to stay?

Plan accordingly with detailed leases on parties, number of occupants, no smoking,  quiet hours, etc. so it doesn't degenerate into a frat house.

The only other idea if the ozone machine doesn't work that I can think of is calling a water damage / smoke damage restoration type company.