The default is -0.1 and some say 0.1 is better…thanks for your advice!
Price gap is gap between spot and market. If you open with positive, it means futures market is higher. Since your futures position is short, higher price will make your entries better
Opening with positive high gap and closing with negative is very good, but it will be covered by several funding fee if you failed to get perfect position. So not really worry about that i think
You can try to open with higher gap and wait a bit