you forgot to tell us what is the vertical aperture (vertical HPBW) of the antenna !! 6, 8, 12 ??
assuming the V-HPBW = 8°, a total downtilt of 12 degrees should help do the trick (the antenna coverage with 12 degrees tilt at 12m high is about 100m).
With 10 degrees, you’ll have 120m theoretical coverage, but because reflections on buildings, it might go beyond 150m/200m.
But don’t reduce the power unless you feel it is necessary. Micro BTS already has a low EIRP, and reducing it further more might impact the indoor coverage.