Adding multiple candidate child records using grid edit

I have a parent table (RFQ) to which i want to add multiple candidate child (CONFIGS) records. I have created a form where the parent table header is created and saved. This includes an [RFQ ID] and a [LEAD VEHICLE] field. If Edit is then selected, a grid edit form of the child records is opened, this has been filtered (using a Formula URL field on the CONFIGS table) to include only obviously relevant candidates from the CONFIGS table. 

I have two issues

1. The CONFIGS records include a field [Lead vehicle] and the RFQ also has a [Lead vehicle] field. I only want to present matching CONFIGS records in the grid edit. 

2. On the grid edit i can present the field [Related RFQ ID] which is derived from the [RFQ]->[CONFIGS] relationship and add records to the RFQ by selecting the appropriate [Related RFQ ID] from the dropdown. However, i really need to only present only the current RFQ ID we are working on.

I'm sure this will make little sense without further explanation! I've tried my best.

Thanks for any help.