Personally, would not go with a bow
drogue. If conditions are bad enough that you cannot sail, it is dangerous to have the bow into the
wind. The wave action will throw the boat stern first into the wave trough and puts extreme pressure on the
rudder. Your spade
rudder boat is particularly vulnerable to damaging the rudder in those conditions. Many
boats that have used the bow
drogue routine have ended up with a disabled rudder. Way better to drag warps or drogues from the stern with the storm jib sheeted in hard as a stabilizer. In EXTREME conditions, sail down the wave at an angle in EXTREME conditions. Read Moitessier's "Cape Horn, the Logical Route" if you've never heard of doing this.
As far as the deck fitting for your staysail, a beefy beam laminated in place or a couple of hefty pieces of
plywood laminated to the deck that will carry the load out to the
hull should do you just fine. I wouldn't halve the 'J' measurement for the deck fitting, would put it somewhere around 2/3rds 'J'. You can get a sail that's large enough to give you effective drive when the jib is struck but you still want to sail. It will also be a great sail for reaching conditions in conjunction with the jib. You could put reef points on the sail and use it as a storm sail. If you wanted to put
roller furling on it, could furl it down any size that you want though I'm not fond of r/f on staysails. Might want to consult a N/A to figure out where exactly would be the best place on deck to locate it to balance the rig.
Running backs should take care of any pumping that you have with the staysail. Using
Dyneema or
Spectra line for the runners and the staysail stay. Might even be able to get by using deadeyes rather than blocks or levers to tension the stays or at least the staysail stay. It takes very little tension on the staysail stay to pull the mast out of column.
If you want to be careful with your main. Would reccomend a Storm Trisail. They aren't the best setting sail but some sail aft of the mast is necessary for a boat to go to windward in serious winds. A third reef in the main will give a much better setting sail but you risk damaging the main. That is the real reason for a storm trisail. Last thing you want is a destroyed main with several thousand miles to your next landfall on an Island without a sail maker or
repair possibilities.