Well, the shoes aren’t the problem, so we’ve made progress!
Sir Duncans and Imperials are really light and easy to overpower, so make sure you are throwing slow and not doing anything interesting with your elbow. All shoulder. No wrist. Or elbow.
46 inches sounds really short. You got any other string? 54-58 inches would be better. You can get halfway descent string at Menards:
I’ve seen it at grocery stores also…
In the meantime, try holding the tip pointed out away from you when you throw.