
To throw flat, keep your shoulder plane parallel to the ground and experiment with your pull line. Try pulling level at various heights (waist, stomach, chest). Experiment with more than just flat lines, also try starting out low and finishing at different heights. You need to exert some control over your arm while still keeping it loose, it's kind of flailing right now.
Slowing down the start of your pull will promote better timing, your acceleration is peaking a little too early. It also might make it easier to know what trajectory your arm is heading on.
You have the makings of good form, keep at it.



