Hi Tony
Your doing well mate
Tricks come with practice
The split kick you tried in the other vid is only small due to you lacking confidence in it
Split kicks and straddles for me seem to rely on the bounceback you get when you kick out hard
Hard to explain but when your legs reach the end or a kick they sort of bounce back due to the tendons being stretched
Try the tricks you want to do on a trampoline if you have one or one of those trampette/rebounder things (they are very cheep)
Keep at it and you will be doing tricks in no time at all
Jason