Is the bearing known that AE was flying from on Lae to Howland Is?
There wasn't one bearing.
If she was approximating a great circle route (the shortest distance between
two points), she would have flown a number of different bearings, as Lindbergh
did across the Atlantic.
And the next bearing chosen after finishing a segment would depend on
dead reckoning about the degree to which wind might have blown the
plane off course during the last segment--or last several segments.
Also, what were the weather and light conditions that were in the area of Howland Is in the morning when she disappeared?
If I remember correctly, it was cloudy only off to the northwest. That's why the Itasca sailed off in that direction post-haste, thinking that if AE and FN had been anywhere else in the sky, they'd surely have spotted the island.
Links to several articles on this page that deal with the scene on the Itasca.