Well, i'm not familiar with sprite collisions and sprites in general, but i can help with the circle pad. to use the circle pad, you use a function similar to that of touch screen's function and button().Use the command
STICK OUT SX,SYthe X-Y position of the circle pad will be within the variables SX,SY. The variables range from 0 to 0.86, so if you want to make a sensitive input through the circle pad, you can use variables between 0 and 0.86, but it only goes to 0.86. The actual value is 0.8666666... im not sure why they chose this value, but if you're fluid enough with math, you can multiply the variables by 1/0.86666... to make the variables max out at 1, instead of this odd decimal number.