Thanks but in ([Date]) doesn't work. The problem is that measures are summed, not calculated for each dimension. Using projected function as "delegated" sort of works for only one part of the union query.
You probably meant "Where ([Date] Between ...)" to separate Weekly figures from YTD. Yes, that's the plan but I can implement it when I get one side of it working (Weekly or YTD). Adding a date in the query now simply inflates the figures.
Please note that in the SQL above I can remove the Date field and the result will be a percentage between 0% and 100%.