Inserting rows and autofilling with functions depending on merged cell and positions

Hello,

I am trying to create a sheet that will auto-calc my estimated costs for a project I'm working on.

I attached the example excel herewith.

My input would come as 4 columns, with the first column being a merged cell.
Depending on these merged cells, I want to input rows and autofill certain values.

Ideally, I would like to automate all steps I added to my excel, however, I would already be happy if someone could comment on parts of the process (hence why I broke it down in steps, maybe we can puzzle together answers )

The function in step 5 is a custom defined function.

Please let me know if you have any questions, I'm happy to get any help on this I can get

Thanks a lot,
Kobe