Hi,
It's going to take a while to get used to this faster type of spinning. Focus right now on control and being centered in your circle that you've stepped into and your correct posture. One of the most important things about the scratch spin is being centered at the beginning. You want to step into the circle, not outside of it and you want to have a bent knee but pause and then straighten that supporting leg you're spinning on. The key is to take your time when you're stepping into the spin. You're really doing a 3 turn and then spinning so take your time with that and use it to get balanced.
You also want to be on the ball of your foot when you're spinning and the best way to practice getting there is by spinning with arms out front in a "v" and with your free leg out front, foot not turned out but toes pointing forward. Don't bring your free foot in as you would normally with a scratch spin, just let it stay out suspended in front straight and get used to that feeling. Concentrat on getting your balance on your supporting leg and not rocking. There's a tendency to lean back towards your heel or rock back and forth at first and this will help you get where you want to be. At this point, the speed isn't going to scare you as much. Practice this part of the spin over and over until you feel secure and balanced.
Once you feel like you're comfortable, then attempt to draw your arms and free foot in to finish the spin. Drawing them in is what causes the momentum of the spin to increase so do it slowly at first until you feel more daring. Just keep practicing over and over and in time you'll get much better!