First, my apologies. I spent a lot more time looking at your dB and realized the "Related Tables" appear to be multiple copies of table "PGASC02" (because of the repeating fields)and are Look up Tables.
Only the table "Gas_Notes" (with its repeating fields - which should be redesigned) is a related table.
Your design is not how I would design the tables. I shouldn't have said "Bad design".
My tables (99.98% of the time) have a PK field of type Autonumber. See
Microsoft Access Tables: Primary Key Tips and Techniques
I have been working on your dB..... if/when I get time I'll post it. I have deleted all of the records just to make it easier to add/change fields/relationships.
It looks, to me, like "PGAS000" is the main table. See if this helps any.
There are 70 fields (if I counted correctly) in the table, so I had to do a little cutting and pasting to get all of the fields in the image.....
Attachment 43463