Btw, I think you must have some Primary Key in your Main Client Database table - in case it is not a composite Primary Key, it essentially must be ProjectID.
It is possible, that you have several projects (simultaneously, or distributed in time) for same customer. When this is the case, then you must have separate fields e.g. ProjectID and CustomerID (simply having customer name in table allows typos when entering the name), and notes must be probably linked to ProjectID, not to CustomerID.
Code:
We basically enter every single piece of info on the client in the table titled "Main Client Database".
This will work until you have a single row for client. When you have several rows for client, you have to enter the same info again for every row - without any typos! And Access will not assist you in avoiding those typos.
With separate client registry, you enter the client info once. and whenever the client info changes sometimes, you update the client info, and it is available for all entries where CustomerID is stored (of-course when you need the some customer info at entry time to be saved and remain unchanged in future, then you have to store this info as value instead of CustomerID).