youtube videos for mark rippetoe squat form. You should find videos of him and his trainees doing squats. Try to get your form just like that. Have friends video your squat so you can watch it and evaluate (and/or post it here).
Stick to a routine (I guess the GOMAD - Gallon Of Milk A Day - and 20 rep squats that you're doing now), and use a logbook. Write down every workout, weights used, details. Try to increase weight by at least 5 lbs every time you do the exercise again.
Track your eating too. Keep increasing calories a little each day. You need to eat like it's your job. If you are ever hungry...you are not trying. When you get full, drink a shake. You should always be so full you are at least mildly uncomfortable. You do want to gain weight, right? With your metabolism/age, you won't have to worry too much about keeping a super clean diet either.
Don't over-analyze, just do the work. Don't worry about your (so called) "lagging bodyparts". Right now all you have are lagging bodyparts. You have to build a massive base before you can worry about chiseling out fine details. Just get big now. When you get to the point where you have at least 3 lbs per inch of height (so for you about 215ish), then you can worry about bringing up lagging bodyparts...and really that should be more like 3.5 lbs/inch of height.
Now, go...and DO.