On the snatch, there are two major things going on 1) your hips are too HIGH, and 2) your weight is on your toes instead of your heels and hips.
1) Your hips are too high because as soon as you start the pull, your legs are already almost straight:
You are over the bar but you need to lower your hips so that your boobs are trying to face the wall instead of the floor. This means that youre going to have to arch back way more than youre currently doing to make sure that you stay over the bar.
Check out this vid:
YouTube - CMG training 020508 MB 2
You can see that Im trying to lift my chest up high so that its not completely facing the floor. This happens by really arching the back and squeezing the shoulder blades back, pretending like youre at Muscle Beach.
2) Your weight needs to be further back toward the heel of your foot. Otherwise youre going to keep rolling forward like this and you will keep needing to take a step forward when you stand up.
Note that by being on your toes, youre compensating by using your arms during the pull. Also not the distance between you and the bar, there shouldnt be any while youre extending. I wouldnt worry too much about this shit, its just something to note. Focus on sitting back and get a better start position and you probably will fix this on your own.
On your cleans, the start position is better simply because the clean starts higher anyway. The thing is that youre still not on your heels during your clean so its in front of you.
Also, when you do a quarter squat, your butt does have to go back as if youre initiating a squat. Because the bar is in front, youre just bending the knee when you catch:
Jerk looks good, but you have to split farther by dropping more.