Enhanced bones are stage 6 technology
on your scale via use of drugs such as alendronate & calcitonin in conjunction with training. Actually, this is almost stage 7.
Enhanced musculature is stage 5, via the use of gene therapy to increase the production of IGLF; mice have gained 37% muscle mass in this fashion.
To reduce damage from high impact strikes, martial artists develop THICK callus layers; the martial arts advisor on _Matrix_ has knuckles that look like the striking surface of a hammer. Level 7, overall.
Enhanced reaction time will result from enhanced musculature, to some extent, & from simple chemical stimulants. Lvl 7.
Martial arts training to coordinate all of the above; lvl 7.
All this combines to produce a person able to punch thru a wall if
exerting full power. It could basically be done in a few years.
To produce someone able to do this *casually*, level 3 or 4. Muscle
spliced with spider silk are probably the best path for this approach, with muscle arrangements based on chimps (not too dissimilar to humans but *much* stronger)
with appropriate bone strengthening chemical treatments as above.