Dear Lal,
Regarding gati/anusaya being located in the hadaya vatthu—not kamma bhava (bija)—I came across another post, Manomaya Kaya (Gandhabba) and the Physical Body (I bolded the part in question):
“The remaining kamma seeds are all “tag-along” in the new bhava, and one of those will rise to the next bhava or existence; the same ‘gati’ are in all seeds.“