At times during recording a vocal part I'll hit a note just a bit too hard and when I play back the recording there is a sharp sound at that point in the recording. Is it just a matter of keeping the recording volume down, or is there some setting in the MMM premium 16 software that can help with that problem?
Ideally, what you need is to run your vocals through a compressor/limiter/de-esser before sending the signal to the computer.
A limiter does just what it sounds like - limits intemittent peaks. A compressor not only brings down loud parts but also brings up the soft parts. If overdone, this can also remove any dynamics as well. The strength of these effects can be set so as to avoid any undesirable results.
MMM has a built-in compressor/limiter in the Audio Effects Rack. Unfortunately, it is not capable of doing this in real time. You can only apply these effects after the fact. So, once your vocals are distorted, there's nothing that can be done to fix it.
As you said (without investing in more equipment) your best option is to cut back on the input level while recording and/or sing a little softer and more consistantly. However, this may limit the dynamics and "expressiveness" of your performance. Moving further away from the microphone is an option, but it's best to stay fairly close. A pop filter is always a good idea.
Perhaps, you can stay close to the microphone most of the time and lean away slighty during the loudest parts. It may not be easy to do while trying to concentrate on your vocals, but it may help retain the character of your vocals without creatimg distortion.
It's possible your microphone is not of high enough quality. Can you tell us what you're using and how it is connected to your computer? Perhaps someone can help you if your equipment is lacking.