your strength won't increase if you move the weight slowly... strength IS all about power = speed with which you move the weight... this doesn't imply break down of form though.
if you work on increasing your weights on deads and bent over BB rows your back is going to grow... i have seen so many guys in gyms get stuck lifting the same weight every week give or take a small change and then wonder why they can't seem to get bigger/stronger... it's not really rocket science - lift more = grow more (obviously provided eating is correct). the other thing that should be mentioned is how many times do you train... are you doing a body part 1x per wk "split" or are you training mostly compound lifts multiple times per wk? the latter gives better results (assuming your not on juice, in which case even a crappy stimulus causes some improvement).
also for chins, i assume your doing these weighted?

BTW, the 3 exercises i mentioned are the best mass/strength builders. there is no other magic do less gain more exercise. oly lifting will also improve your back thickness and if done with correct technique (or as close for a self taught amateur) can be good fun too... unfortunately most gyms discourage it or simply don't have enough space or are too crowded.