First, I'd suggest that you try not to lean so much to the right. The cross step can help get your hip out of the way, but it look likes you are using it to compensate for you not getting low with your legs. This can really tweak your back out. PLus like you said, it's too late. Also use that balance arm to keep yourself aligned. It has it's own path as well. It travels from ball to in front of slide leg, to out in front of you, to it's final destination out to the side in one fashion or another.
Secondly, your swing plane is off. Watch the last shot from the front. You push it a tiny bit out to the right and pull it back behind your back. Try letting it free fall. Plus the bending to the side and the open shoulder isn't helping either. Because now you have to move the ball with your muscles instead of gravity to get it to catch up to your feet. At one point I thought you were going to swing the ball into your trail leg. No wories though. I ended up looking like this and had to straighten up more. Try dipping the shoulder a little, but keep your back straight, and bend at the knees. It does wonders mate. Additionally, like you said starting the ball earlier would definately help. You could try switching to a 5-step or a variant like mine (slide with left foot and then a 4 step approach). You'll already be in motion and can start the ball on the next step like you are already doing. The tricky part, getting used to a 5 step.
Third, don't turn your wrist over so early. This is something I'm still struggling with so no worries. Anywho, you're losing a ton of leverage out of your release. On the front and back shots you can see it pretty good. And by the time you release the bowl you're on top of it.
Fourth, a slide could definately help. It probably wouldn't make you look so much like you are moving along at a nice pace and then your caffiene all of a sudden kick in so you speed up. Plus the big thing for me, as always, is planting like that may generate a lot of power, but some water or food on your shoe and goodbye knee. It seems to me that when I slide, I get my body weight distributed throughout my leg with a majority in the quad and hamstring. When I plant or get stuck, I tend to have all that energy and body weight forced onto my knee. Additionally, it feels like more of my momentum and energy is transfered to the ball, but that may just be me.
Those were some things that stood out to me. I thought they were a bigger issue than some of the others. For the most part, decent Cranker plant and pull technique. A few areas of work but some practice could clear them up. I was just wondering if maybe you are tyring or thinking too much. Or even if Cranker is what you are going for.
As for some of the things you pointed out. The foot being off the ground, no biggie. TJ and WRW Jr. do it all the time, so does Scott Nolen and Chris Barnes occasionally. As long as you are smooth and clean at the line it's not a big deal
. Backswing height is no biggie as long as you aren't forcing it to the point where you are completely vertical. Norm Duke and TJ have two very different backswing heights. I say, as long as it's free, no biggie. I like where your ball is positioned. I would like to see your non-swing hand underneath it to support the ball weight and get some tension out of the swing arm. All in all, at the setup, the ball looks to be in a great spot, especially, for a swinging-hinge pushaway. And being straight up can be fixed with a little bending at the waist and knees (mostly the knees). Act like you are going down an escalator behind a couch for your niece, nephew or whoever.
One thing that helps me is watching the pros. For pointers on my form I typically, watch bowlers who I bowl like. In my case, David Ozio and Chris Barnes. Additionally, I like to watch the female bowlers because they can't out-muscle a 15 or 16 pound ball like the guys so their technique is more sound.
Anywho, I hope this makes sense and helps. Sorry for the length.