Does a dead hang increase pull-up strength/help me work up to pull-ups?
It does help by improving your grip strength and tolerance to hanging/having your arms overhead, but it won’t directly improve the pulling strength you need - for that you’d need to work with easier pulling variations - as it is in the routine https://www.hybridcalisthenics.com/pullups - whether that’s assisted pullups, horizontal pullups (rows), or other forms of pulling motions - see this too in case those aren’t an option :)