Regarding the pedal feeling squishy, those pedals have adjustable spring tension. Look a hex bolt on the back of the pedal and turn clockwise to increase the tension. Increasing tension should make you feel more secure, but be cautious about increasing tension until you are more confident in your use of clipless pedals because it will make it harder to clip in and out. Beyond tension, make sure you aren't inadvertently turning your foot during your pedal stroke as that will cause you to clip out.
Regarding numbness, padding (on the inside) isn’t really the solution, it means you are carrying weight on soft tissue rather than the bones of your rear end. That could be a saddle position issue or a more general bike fit issue. Tell you LBS you are having the issue and have them adjust your fit. Lowering the saddle slightly and tilting the nose up just a little are two easy fixes you could try. A wider saddle might also help.
On grinding noise, not sure what that means. Is the chain hitting the cage? If so, and you are not in trim position, try increasing cable tension.
Last edited by DOS; 05-07-19 at 11:39 AM.