How to best recover from an excessive descent?
Sideslips at high G and/or high speed aren't a good idea structurally.  

Absent a G meter, airspeed and judging G load is all you've got.  If I found myself going straight down at 100 kt, I would try to keep the speed below maneuvering speed, 128 kt, but if I felt I was applying too much force and risked an accelerated stall, I would let it go faster and if the air was smooth I'd let it go up to Vne if necessary.  

And in a really extreme case, if the choice was exceeding Vne or maybe pulling the wings off, I'd take my chances exceeding Vne.  If you have to exceed a parameter, it's safer to go too fast than to pull too hard, because there is ample safety margin for flutter, and you know how much you are going over.  

Of course, without a meter, with G load it's all judgement.  The yield G limit for normal category is 3.8, so what can be really useful is go with your instructor and practice 60 degree banked level turns to become familiar with the sensation of 2Gs, which will at least give you a reference point.  Even better if you can get a ride in an aerobatic airplane and learn what 4 Gs feels like and try to stay below that when the time comes.

The other big thing is knowing whether you are in a dive inverted or right side up.  This is a problem for pilots who get flipped over by wake turbulence and end of upside down in a 45 degree dive, and instinctively pull right around in a split S through 90 degrees and rip the wings off.  In an inverted dive most airplanes will accelerate past Vne in a heartbeat.  

If you are in an inverted dive like that you have to roll the plane right side up before pulling out.  Recognizing it takes training and professional pilots often get upset training in aerobatic aircraft to develop the correct reactions.