It will take you less than about 30 mins to start walking quite confidently on them,so don't sound so worried!
Make sure you
adjust the knee bar so its right for you see - I know you have skyrunners but generally speaking most of the info on the forum will be tranferable to any jumping stilts you have. Just double check your manual just incase its slightly different.
About the gap check out the the first steps link in my signiature theres info in that thread which will help and also check out the topic on knee straps in the FAQ.
If you are above 5ft and over 45kg you're fine on the adult ones!
Its a bit off topic so I'll move your post & this answer for you on its own thread