"So...if I combine, do I get rid of the queen in the weak hive? Do I use multiple sheets of newspaper? Do I slit the paper a lot, just a few places? Basically how do I combine them? "
Short answers, Yes the queen has to go. One sheet is sufficient, small, few splits, otherwise they combine before they get used to each others sent. Then lots of fighting at the entrance, ignore it , it's a done deal, they'll get over it. Combine when there is no rain forcast, otherwise it will wet any newspaper hanging out and wick inside and fall apart immediately. If the breeze tries to blow the paper off, have a little masking tape ready to hold it down til you set the other hive on it. Don't know what else to tell ya, it ain't rocket science (we are on the wrong coast) or I couldn't do it.
Small hive survival, how much pollen do they have stored that the larva didn't ruin? The workers won't let the queen lay unless there is enough pollen to support the brood no matter how much you feed them. Not really much time left to lay and mature before the Jan. fronts start rolling in here.
I don't think you got the BT to bottom of the open cells, other wise the larva would not have grown to the size you described after spraying. They just went under it.