Well, after daily practicing of my draw with the leather tab, my thumb no longer feels like I'm stepping on it.
I've learned to press the tip of my thumb firmer against my middle finger and the index finger is no longer pushing my thumb against the string so heavily.
I still can't pull all the way back to a full Korean draw but I can anchor and hold with the thumb right behind my jaw (similar to my mech. release anchor) for 10-15 seconds w/o trembling. Still need to practice and improve my strength/endurance.
Note to bluelake: Do you still offer thumb rings for sale, if so how much?