Is it unethical to expect one's PhD students to work after graduation without compensation? Should graduates ask for compensation for work?
You are thinking about this like an industry employee (which you are, so that's a reasonable stance).

Your advisor is thinking about this like an academic (which they are, so that's a reasonable stance).

Some perspectives:

Academic work is personal work and community work

You don't work for someone in academia as much as you work with someone. It seems like you are feeling a lot of conflict with your advisor right now, but I'd step back a bit and think about whose research this is. Certainly at some level your work benefits your advisor, but isn't it your own work, too? Do you not want to see your results published?

Is your advisor making decisions about suggesting further experiments that pushed your timeline beyond what you hoped because they are getting free work out of you, or are these steps to make the paper better and importantly to make it publishable (see below)?

In academia, it is normal to work on projects from a previous position; in industry it is not

Almost every academic will, at any time they move positions (including graduating as an undergraduate/graduate student, between temporary positions like post docs, and when getting hired as a professor and any moves afterwards) have some unfinished business at their previous place of work.

It's not reasonable to expect every research project to fall neatly into the academic calendar, conveniently finishing right at the conclusion, especially given the unplanned timelines surrounding peer review. Therefore, people tend to spend part of their time in their new position finishing up things from their past one, while being paid only by the new institution.

This gets "paid forward" in the future when the same happens during the next transition. A frequently asked question here at Academia.SE is some version of "which institution/affiliation should I list on this paper, new or old?" because of how often this happens.

Unpublished work is worthless to you and the academic community

Maybe your work is in a thesis in some draft form already, but all of the work you've done that isn't published is doing nothing for you or for academia. Maybe you're fine with that, because you aren't an academic anymore, but ultimately whatever funding agency funded your research and the university you worked for did so because they wanted you to produce published results, not just to give you the PhD title. If you think there is value in the work you've done, then that should be an incentive to get it into a form that can be shared.

On the other hand, you may decide that publishing is not actually of any benefit to you. If you don't feel intrinsic worth in the project, and if you don't plan any return to academia, then probably one more published paper won't mean anything tangible for your CV.

Given these differing perspectives...

I don't think there is any fixed answer. Should you do work for a past advisor without compensation? No. Should you collaborate with people you've worked with in the past to share your research with the broader academic community? Probably yes.

Ultimately it's up to you to define where those boundaries are. Personally, I would think it to be irresponsible to fail to follow up on basic authorship duties like responding to reviewer comments, editing manuscripts for submission, etc. These activities shouldn't replace paid employment, but they can be completed in a few free hours during a transition period. Coming in on several weekends to run experiments sounds like a bit much - maybe there is a compromise solution where you can train a new student to run those experiments, add them as a coauthor to the paper, and continue helping with the manuscript(s)?