Totaling a field with matching criteria from an UNRELATED table

This is more simple than I originally thought after I reread your post.

Use two relationships:
 

Add a summary field for the hours in each OT and OT Projection relationship to the Employee:


Then you can add a record for an employee for a specific date and add multiple OT hours and OT Projection hours and use a formula numeric field to calculate the difference between the summary fields:


formula field:


Then you can see a list of employees and dates and you can set up filters for specific dates, departments, etc...