Well... though I do not know the exact solution of your problems as it is long time that I am away from DSP world. Anyhow few years back, I was too at your position and really curse the PD tool a lot with my friends ..... that what the hell this PD is ....:) there is no main function as we are often familiar with C/JAVA etc... it is a different world but believe me after a very short period of time, I found it very interesting and simple to program in PD. so just gear up yourself, it is new world for the orthodox programmers but very easy world. I must say.
Now come to the problem one by one. suppose we want to calculate the amplitude of voice. Do the following steps. ( some senior/junior DSP programmer can correct me, if I am wrong)
step 1: Use the adc~ object to take input
step 2: perform the fft~ to convert the input into a complex number
step 3: calculate the magnitude by using the formula sqrt (real*real + imaginary* imaginary). you have to use the object +, * and sqrt for this purpose.
step 4: show the output in some display object.
step 5: try to learn write this info by using write~ or some other kind of object into file.
step 6: use the dac~ object in the end to listen your voice...