I do not have right version to open the dashboard attached. I will answer from what I understood from your question.
I guess your calculation of # Orders is complicating your overall situation.
Considering your data is like this
You can create count distinct as #Orders instead of the function you are using.
To get market share , now use any of the options you mentioned in the question, you will be able to create a field which gives you market share. Only thing, you need to make sure your table calculation is table(across) since company IDs are placed across the table.
Hope this helps
Jeevan, thanks for taking the time to answer my question.
You got it almost right! The only issue is that I can't do a COUNTD([Order ID]) since I have only one consecutive order id per week, like the image below:
So, I need to first do the calculation to obtain the number of orders placed in a week (# Orders) and then obtain the % Market Share :/