Assume wind blowing directly from north to south. The target is 45 deg off from due north.

Where is the Kestrel pointed - due north into the direction of the wind, or off 45 deg in the direction of the target? If it is pointed at the target how is it held - vertical as if you are viewing the target through the wind vane, or horizontally on its side?

If the Kestrel is pointed at the target instead of directly into the wind, will the wind speed reading reflect that and give me a wind speed that requires no further adjustment?

I think that the kestrell with the ATRAG and FFS requires you to take 2 different readings. One into the wind and one facing the target and it will calculate your proper wind holds

Measure the actual wind speed and the angle in-relation to your line-of-sight.
More importantly is to guess what the majority wind condition is between you and your target.
Enter that into the ballistic calculator.