@onoff48,
First, congrats on trying to help otherwise homeless critters. :-)
Second, any rescue organization or shelter that you're fostering for should have provided you with insight and training on how to introduce the fosters to your own dogs. I'm disappointed that they didn't. That would have helped you protect the dogs from each other, especially your dog. EhBeth gave some great advice here. And Kuvasz, even though it sounds brutal, is right when he/she says do no harm to your critters.
I've also observed pack behavior (when my other half and I got married, he brought 4 dogs into the union), but not as long as some here on A2K. Spouse and I now have 6 in our pack, and I've learned from spouse and from the dogs that the human is the alpha, and you need to accustom the critters to that from the start. One of the ways to do that is to put the most dominant dog on his back and make him subservient to you (and other two-leggers in the house). I'm lucky . . . the 4 "kids" that my spouse brought along with him quickly accepted me as one of the alphas. I've also intervened in critter disagreements and in that way have been able to assert my alpha status, too.
When we added the two puppies to the pack through adoption, we made sure that they knew their places in the order by feeding the older dogs first, and feeding them in order of pack seniority. That helped reassure our 4 that they came first and that the puppies were lower down in the order.
Hope that helps. ;-)