The questions you posed are some of your faults (which is why I think you listed them).
First, you need to lead out with your chest. It doesn't look like pulling power is an issue; you look very explosive. However, you need to lead out with you chest A LOT more. Your back is almost parallel and your shins are perpendicular to the ground when you start, almost like you're trying to deadlift the bar up. While the goal is to load the hamstrings during the first pull by getting the knees out of the way, you need to start with the chest taller, butt farther down, and knees slightly over the bar. You need to PUSH THROUGH the ground rather than PULL OFF of it. Incorporate those big muscles in the front of your legs (your quads) when you begin your ascent. The classic lift pulls are not deadlifts. You can help this by doing snatch deadlifts with a pause at the knee to help you feel proper positioning. Simply cueing yourself to keep your chest up (while keeping the chest and shoulders slightly over the bar) will lead to your butt going down and your knees going over the bar, all while building tension across all of your entire leg(s), not just the hamstrings.
Second, continue work on your receiving position. It looked like the third snatch simply surprised you. Do you consistently hit 90% of the 225 (205-210)? If the answer is no, and if the answer leads you to identifying that you lose a lot of your lifts because the bar jolts you, then you would benefit from overhead work. Depending on flexibility, you can do close-grip overhead squats, along with snatch presses/push presses, to strengthen the muscles involved with the receiving position. You can also incorporate snatch balances to simluate as closely as possible the weight coming down on to you during the snatch.
Lastly, I would revisit where your hands are placed on the bar. If you have to bend them, then there are not in the right position. When the bar is in your hands and you're standing tall, the bar should contact you at the hip crease. You say a collar-to-collar grip is forcing the bar to contact you at the belly button, and in the video it looks like you're pretty close still, so you're just going to need to find that grip that lets the bar connect with you at the hip crease. Once you find that, you're going to need to break that habit of bending the arms. This WILL take time, so be patient and give it the proper attention it needs. Tall, dip, blocks at mid-thigh, and mid-hang snatches will help with this. You can argue that there were/are a couple of lifters who were/are successful with an arm bend (like Mario Martinez, 1984 Olympic Silver Medalist), but they either a) start their pulling with that arm bend to shorten their limbs and don't bend it any further during their first and second pulls, or b) have a fault in their lifting techinque that they just learned to deal with (like Rich Froning). However, most would argue the people that fall into the "b" category could be much more successful if they learned the proper techinque. Is he strong? Yes, but I believe he and others that do this could lift a lot more if their strength was applied more efficiently.
I hope this helps. I think your speed under the bar is fine. It looks like a long laundry list of things to work on, but one thing will lead to another and you'll be doing a lot better if you put the time into correcting your technique.
Javier A. Sanjuan
Olympus Barbell Club
Dear God, please help me lift heavy and be awesome. Thanks. Amen.