How do I roll back 1.4.4 to 1.4.3.5 for testing?

I don't remember exactly but if there are database changes you probably cannot directly.

The recommend procedure would be to use the backup to backup the database. Then install the older version and re-run setup.

Then if you upgrade you could import the backup again.

For testing I would recommend to setup a 2nd site. (of course never update a live site before testing that everything works with a test site).