OK, so that wouldn't be 3D Touch. 3D Touch is when you press and hold harder on a particular icon or app - it doesn't interact with a keyboard at all. When you do that, a separate menu will come up with other options that you have.
Try doing these things:
Go to Settings>General>Accessibility>Touch Accomodations, turn on Touch Accomodations. There you have the option to turn on Hold Duration to allow you to hold down your finger a bit longer or a bit shorter in order for the tap to be recognized. You can play around with this setting to see if you can set it more to your liking.
Just below that, you can turn on "Ignore Repeat" to prevent inadvertent multiple touches from causing the selection to be repeated (if your fingers are shaky, for instance).
Just so you know, this is what you might see if you were using 3D Touch. I placed my finger on the Notes icon, then pressed down a bit harder on it to get this secondary screen:
So, as you can see, 3D Touch is an enhanced set of options that you access by holding down a bit harder on an item. It doesn't cause numbers or other keyboard input to repeat.
Best of luck,
GB