I dive double HP120's. They are approximately neutral when empty. I use an additional four pounds when diving dry. I did the bladder failure in fresh water using only the dry dry suit. The dry suit helps but until you get to the surface, it is a hard swim. Once on the surface you can over inflate with your arms in front and and this will get you to the shore or ladder.
With a 3mm wet suit I am extremely negative. I do take with me a 50 pound lift bag and a reel, but the real saver is a fully closed SMB abount 8 feet in length. It has a push to inflate (or deflate) mouthpiece. If you have the presence of mind, you can partially inflate it and place it under both armpits (like a swimming noodle) and control your ascent with the push to deflate noozle. Once on the surface, if not already fully inflated, you can inflate it fully and continue to float on it while it is under your arms. Do this with your reel attached just in case!
This takes practice! As to a lift bag, I would attach the reel only as a life line. My experienced with using a lift bag is to put one arm through the bottom loop(s) that the reel attaches to. I personally use a lift bag with a dump value that can be operated from a line at the bottom of the bag.
Practice in a pool. Then do it at 30 feet. If you can do this at 30 feet, 100 feet should be no different except it will take longer (hopefully much longer). BTW,. have you ever ditched and donned the doubles? Not as easy as it sounds.
As to hands being ripped by small string, I always wear gloves. Even if the divemaster or conditions will not allow, I stowe them on my person anyway. Ever tried to hang onto a drift line in a ragging current with 10 divers ahead of you?
