Current state of Household Membership signup (Wordpress)
This question has a lot of moving parts, not all of which are clear to me here.  It may be best as separate questions.  I'll try to answer the parts I see.


It sounds like you need to track the members of a household each as a separate contact.  This is best with Webform-CiviCRM.  However, Caldera Forms will do most of this.  You can create several contacts, and create relationships between them.  However, you can't take payment on the same screen (not a big deal).  I'm not sure how it handles pre-populating related contacts for managing households later - you'll have to experiment.  Worst case, you could sponsor the Caldera Forms devs for a lot less than 200-400 hours for that feature.
You do NOT need to use the Household contact type if it's not important to you!  You can do this with a "primary contact" who has a relationship to the other family members.  This is up to you.  I prefer to not use households, personally.
You use the Relationship Type feature of CiviMember to allow family members to inherit the membership via relationship to the household (or primary contact).