Like everyone says, post a vid. You have a desktop/laptop but not a camera on your phone or a friend w/ an iPhone?
Since you know what good form looks like, get on a box and go from there. Even if it's just you squatting off the box and just setting yourself down, start there.
I'm doing some work with postural analysis and have learned a lot about the tension and forces in the muscles and how much work you need to do to get things right. If the box squats are ugly drop them and the squats all together, then try these....
Stop sitting down, or avoid it at all costs. Either lay down or stand, that's what our body does the most and sitting down is the last thing YOU need to do. When I say lie down I don't mean with 10 pillows either, the point is to get a neutral back, optimal length in the hip muscles and to help your kyphotic posture and neck issues.
Change your training. This is the most important thing. If you care that much take a (thorough) look through the articles they have on posture. This is by far the best one I have read here, read and do everything they say, if you want to squat.
If you want it fed to you, drop your pressing, mostly. You can do some pushups at the end of a session, with a wide grip, but only to get a stretch and pump so that you can do some serious stretching, DC style prefered. Stretch your pecs, very deep, with soft elbows. Start with R-band stretches with your arm parallel to the ground and work all the way up to a 45* angle, behind you.
Stretch and strengthen your external rotators. Face pulls, row work and external rotations. Also, drop the lat work for the time being, they can cause all kinds of havic, at least now. This means you should be hitting the back at least 2x per week.
You also need to loosen up your hips and strengthen your glutes. Be a man and do hip-thrusts. You can always do cold muscle stretches on your hip flexors, so do it, a lot, meaning throughout your workout and during the day, between sets and between meals. This means you might wanna do less leg lifts and hip-flexor ab work, since that's what most people are doing when they cruch... try some planks.
It may seem like it's a lot of restrictions, and it is, but there's plenty to do while you lift.
I might do something like this:
Wednesday. "dynamic" day-Posterior chain work, GHRs are prob best, include those hip thrusts, no deads though, if you can't squat I doubt you can pull. Today would be the day with some mad pumps and they day you stretch until you hate yourself, hit your hammies hard, then have someone else stretch you if you can. same w your glutes, deeeep stretches.
Friday "dynamic" for back, try those lovely kroc rows in here, aim for 15-25 reps for every set today. Finish off with some wide pushups or flies and stretch your pecs hard.
Saturday. Heavy posterior chain.
If you have any other questions, let me know...