Automated date calculation within multiple cells

Evening All,
I am trying to create a spreadsheet that allows me to track a large number of design documents that my team are producing.
I have managed to work out some of the basics that:
- calculate review due dates by the client
- calculate days over due for issue and review/approval by the client

All good so far but here is where the problems start. I have attached the draft version of the file with 3 questions added as comments to the areas i have a major headache with....... Any help, improvements and advice would be very welcome.

Regards

MG
NEW DRS TEMPLATE DRAFT A.xls