Ditch the Kilz, it most likely will NOT mask the odor. You need Zinnsers Cover Stain ar better yet Bin

Annie it is a rental in a very hot market, and it doesn't make sense financially to have it scraped, as there are other more immediate issues that are necessary, I have a limited reno budget and timeframe in which to get it on the market.

Nicotine is a horrible polluter on ceilings. It also bleeds and prevents adhesion. It needs to be cleaned before primer or paint. A wheel brush or sponge mop with cleaning solution like Dirtex will do the job.

Will a mop remove the texture?
Yuck!

This really depends on how much staining is on the ceiling anyway. I don't think it's realistic to say that just because a person smoked in the home, that you need to do a full blown TSP cleaning before you can paint. Look at the ceiling. Is it visibly stained? Also, try washing some of the walls with a white rag and see how dirty the rag gets. If it stays white, then you really may not have to wash anything, or a quick wash with Dirtex may be enough. Don't forget that TSP needs to be rinsed very well. Don't use that unless it's absolutely required.

As for the popcorn texture, if it was applied and then never painted, you may be surprised how easily that stuff will come off. You may be able to spray it with water using a garden sprayer and then scrape it off....messy yes, but really not that hard of a job. If it was painted at some point, then it will be much more difficult to remove.

There is visible nicotine stains on the walls and ceilings. It is gross. I will certainly wash the walls and test an area on the ceiling in the closet to see if it was painted.

If you scrape it don't you need drywall repair/texture? I forget if the walls are textured but that is the norm in this area.

Sometimes there is a little patching to do after removing the popcorn, yes.

Spray a coat of Bin on it all and you are ready to paint