Uff, these are quite some questions ;-)
Yes, of course one can measure the impacts. There are different tools, starting from conducting employee surveys, customer satisfaction surveys and similiar tools. Further of course you can measure the financial impacts for example regarding the training of your employees and additional qualifications they achieved versus reduced turnover rates, longer staying in the company etc.
There is no ideal way of doing CSR as CSR is very individual to each organisation. It depends what are the impacts of the organisation, what are the expectations of stakeholders, what are the values of the organisation, what strategy is it following etc. Mainly it is about identifying the material issues an organisation has and how to deal with them. The tool to help you identify them and deal with them is ISO 26000.
Good luck
