Greetings
You're rocking back and dropping the hips a bit, so your weight ends up on your heels and your shoulders directly over the bar (look at the profile view). Likely to get the back tightness you speak of.
Get your weight on midfoot and keep the hips higher than you want to. When you execute step 3 and bring your shins to the bar, your hips should stay put. With the bar on your shins, and your weight midfoot, set the back from there. Hang out over the bar, and drive your midfoot into the ground as you hold on to the bar.
I'd also have you bring your heels together a bit so you have more of an angle with the feet.