Virtually every broach I've seen (yes, there have been several) have been due to the outboard end of the pole getting too high. When the pole goes up, the center of efffort of the spinnaker goes aft. If there is enough load in the sail and the center of effort goes too far aft you get a LOT of weather helm which can lead to a broach. In light winds you don't have to worry about it but when it starts to pick up, keep the pole low. Normally you want to keep the clew and the tack at the same level and the pole parallel to the water. The pole should also be perpendicular to the wind.

You should have long enough sheets to allow the sheet to run through the pole and back to the cockpit. 2X boat length is a good rule of thumb. Don't put a stopper knot in either the sheets or the hallyard. If the crap really hits the fan you can just let the lines fly, it's a get out of jail free card. Normally you just let the guy go then gather in the foot while lowering the halyard. If the wind is up I find the best way to drop the spinnaker is to lower it directly behind the main and stuff it down the companionway hatch. This can be a lot easier than trying to contain it on the foredeck.

Have fun!