I agree with ItsMe and June. It sounds like you are not a database person and doing the best you can in the given situation.
In different words, it seems to me you are juggling about 15 balls in the air, and someone keeps adding more balls. At some point, it's all going to crash - regardless of how well-intended you are, or how much time and effort you can possibly dedicate.
There are a few options that may be applicable.
You can do what M$oft and large organizations do. (Actually any large project) That is, scope out a longer term plan of what functionality is required and what effort and skill sets are required to accomplish it. Then break the work into do-able chunks. This is equivalent to 'in release 1 we will deliver a,b and c'. Get something working that is manageable and fits with the bigger plan. Get another team (contract or hired consultant) to map out release2 and initiate development and a test plan. ....
You can't do everything all at once! Something has to be priority. Find it, communicate it and focus on it.
Readers here can help but we need to see what you are dealing with. The current ERD would be helpful; as would any documented requirements/specifications.
Get a Project Manager involved to plan, schedule and monitor tasks and resources.
You need a plan (or plans). What is/are the specifications of this Health and Nutrition Project?
What is the structure of the "Project team"? Who has responsibility for the overall plan?
Who is setting priorities and managing work loads? Who is handling communications between WHO officials, this project team and the users? Where is the database technical expertise coming from? Where is the subject matter specialist(s)?
In real life database, YOU DO NOT HAVE TO ADD NEW FIELDS TO OPERATIONAL TABLES PROGRAMMATICALLY ON A DAILY BASIS!
You have to get some help.....