Off course a good technique is important, but its also important that you feel comfortable with that technique.
Also if the sound your producing with the technique your using is good, then I dont think it really matters if your fingers are spread out or not, eventually you'll find the technique most fitted to your hands and mind, and your style of playing.
When practising reverses, you should just relax, if you can play tumbao with the other hand, it wont take long before you can play reverses,( if you practise
).