The fake urchins really only help if the babies can find them. How long has the daddy refused food? They will hold for about 21-24 days or so (If they hold to term)
No need for rotifers, newly released bangaii that have been held to term are more than capable of eating new hatched bbs. I use a hatching decapsulated from Brine Shrimp Direct works well and no shells.
Keep an eye on the papa, if you try to catch him you may force him to spit out the eggs. Not a good thing unless you have a way to incubate them to term. Hatching jars work well.
Isolating the babies after hatching will be easy IF they find the fake urchins...collect them and the urchin at the same time. Other wise get ready to hunt them down one by one and try to get them without damage. Not real easy in a reef.