Yes, the yellow sun is what gives the Kryptonians the powers. That combined with the smaller planet having lower gravity. However, without the Kryptonian genes there are no super powers.
I have read some fics where through genetic dilution the powers are lost in succeeding generations. That will not happen if the genes are dominant.
RE: The aura changing the Earth human physiology - That was the only way I could think of that could explain the dificulty in acheiving a pregnancy.
If you continue to follow the series it will be explained in greater detail.
I am further along on the LCFicmbs board. I will be using an accellerated posting schedule here until I have both boards at the same point and then I will be posting two chapters a week, Tuesday and Friday.
I am in Volume 2 on the other board.