I had ridiculously high levels of NK cells and now have aone year old playing in the next room.......so yes it can happen. I was on the same protocol as you prescribed by Dr Sacks but implemented by my FS here in Melbourne. I actually stayed on the prednisone between cycles at the level of 10mg after reading some research by Alan Beers and it was our second cycle that I fell and stayed pregnant. The book "Is my body baby friendly" by Dr. Alan Beers might be worth a read for you.
As for IVIG treatment I very much doubt you will be able to get approval to use it in this country as IVIG is a very very scarce and expensive treatment and you have togo before a panel to get approval for use...IVF is not an IVIG approved criteria in this country.