Apply conditional formatting to multiple cells merged on a row from a data merged row

you have discovered why 'merged cells' are not used on any well constructed sheet that manipulates data - they should have never been implemented into Excel - their only purpose is to make the sheet look 'pretty'.
the only cell that is active in a merged range is the upper lefthand cell.

i have had a play around today
and if you do a few things - you may get the result you are after

1) change the cells in row 3 - to be real dates and then format to show just the day - that will stop things like the 12 in all months being highlighted and only the actual date
2) remove all the merged cells - you can use border formatting to show those groups if you want to , and then you can highlight the 2 weeks if a day falls between

i have used a formula
=IF(ISODD(WEEKNUM(TODAY(),2)),OR(WEEKNUM(TODAY(),2)-1=WEEKNUM(E$3,2),WEEKNUM(TODAY(),2)=WEEKNUM(E$3,2)),OR(WEEKNUM(TODAY(),2)=WEEKNUM(E$3,2),WEEKNUM(TODAY(),2)+1=WEEKNUM(E$3,2)))
to do that , as conditional formatting - may not work , if the year changes over , as we sometimes get week number 53

I have also added that formula in ROW 20 - so you can see the trues and falses - NOT NEEDED for conditional format , just a visual indication of whats going on

Now to test different today's - I have also setup a date you can enter into B1 - to test what happens on different today() 's
thats in ROW 16 - so you can see whats TRUE and FALSE when today() is changed using B1

I suspect that the formula i am using can be simplified by someone more expert

so thats a few changes you would need to make, but it will work as shown in my example attached

I suspect you also want a month indication
which i have not done - simply as this has been a lot of work, and your not interested in making the changes, then i have not wasted more time on a solution
OR
if you want things different

i have not tested for all possible dates , as things may change when you start to implement on the real data - and the solution may not work for you , after all - anyway something for you to think about

If you are not prepared to do those changes , then i dont know if there is a solution, maybe VBA - not my area - as mentioned before i try to avoid using merged cells whenever possible - because of these sorts of issues