If i understand this right, it sounds like you are doing a little skip before u do the vault, as far as that being a problem, well, its not a problem, its perfectly fine, it wont effect your kongs at all. As to your preference of which foot you go off of, thats up to you, if you feel weird going that foot, go to a gym and practice doing them the other way until you feel comfortable, then do then on the normal ledge outside, the move it to a table. If you have a fear of doing it with the other foot, just look at the obstacle and imagine you self doing it right. Just picture your self doing it.