Castlelink allows you to adjust many useful settings, unfortunately throttle endpoints are not one of them. Using punch control and timing, you can make a certain motor a little more drive-able, but a 7000Kv for instance will still be extremely fast. Most modern radio transmitters have end point settings, but Castle specifically recommends against using anything but maximum settings. A brushless ESC works hardest under part throttle operation, and constantly running at part throttle is not recommended. I see lots of guys doing it without issue, but I can't recommend it since Castle does not.

Your best bet would be to pick up a lower Kv motor, and a cheap 3 cell lipo for when you get the need for speed. You should also have an assortment of pinion gears to tune with.