I've had every scenario you've described with your angels. The breeder net doesn't work because even if the fry don't fit through the net the big angels just squish them. I've made dividers with plastic craft mesh and they swam through and got eaten.
The best solution seems to be a tank for the breeding pair with no other tank mates. It's really fascinating to watch them care for the eggs and babies.
I bought some fine netting from the fabric store and used silicone to attach it as a divider in a glass aquarium. (I have some really bad pics of that somewhere if you're interested

) That actually worked but I accidently pulled it away from the glass and made a little opening. It's kind of funny though that when a pair has fry about the same size as the pair on the other side they don't seem to notice the fry coming through are not theirs and just take care of them like their own.
My problem has been once they get to around pea - dime size I start having a rapid die off. I think it has something to do with the tank being to small.