>1. What to do to stop the robbing? or does the robbing screen work well enough to just let it go until they stop on their own.
Shut the hive down completely using screen wire. After the robbers have mostly gone home, open a space just big enough for one bee to get out at a time. You need to do this with screen for two reasons:
The screen confuses the robbers.
A robber screen is fine too, but i would also reduce that entrance to one bee at a time...http://bushfarms.com/beesmisc.htm#robberscreenhttp://bushfarms.com/beesrobbing.htm
>2. Should I add honey frames and screen them back in for several days to discourage the robbers?
Several days is too much. They will need water and pollen and other things. But you can close them for a day usually with no issues if they have enough ventilation.
>3. Is it time to give up on this hive?
I would reduce it down to one bee access with screen wire and leave them alone for a while. They might surprise you. Or they might already be queenless...
>4. Is this the same add a frame of larva each week until the numbers are so large but this approach worries me because two of the hives I combined had been robbed out and were I think fighting starvation. So just adding larva and honey seems like the honey will just continue to get robbed.
There is no point trying to deal with other issues until you deal with the robbing.
>5. Should I open the hive? Does 'local' hive bees break into honey in a different way than robbers.
>I know robbing looks rough.
> But I expect the hive bees would have to access the capped honey for the larva and for the nurse bees. Is there a way to tell them getting into the honey compared to the robbers?
Yes. Robber rip the comb apart. Local bees carefully uncap it.