Well, you'd said:
70 milestones, each milestone can have upwards of 10 tasks with a status, completed by and completed time respectively
So, to me, based on that description, I would assume the schema would look somthing like the attached screenshot. If you need 70 instances by default, you can set that up in the form's default values (data tab on the ribbon) or by saving as source files and modifying the template.xml file (which is the approach I'd take for this, less clicky than using the IP UI).
Then conditional formatting to show specific milestones on specific views or sections or whatever is needed for the layout.