I'm late getting back to you, but listening to your sample, there's nothing low about it. The handclaps are peaking about -4.6dBFS. The LUFS was -15 which is not bad at all. You really can't compare it to your friend's track as his has more instrumentation going on and a better mix. The claps you are using are overriding everything. Drop those down by at least 10dB and you can bring up everything else. (I personally despise those fake handclaps... they are SO overused!) You can put a limiter on that track... anything to bring it more in line with the rest of the track.
Volume is relative, and can be adjusted both going in and once it's in the computer. Putting the gain knob at 12:00 is meaningless, as microphones all have different sensitivities. The criteria needs to be where do you get a proper level in the DAW. If it's peaking at -30 on the scale, you simply increase the gain knob. Bring it up until you are getting the first glimmer of overload on the front meters and then back it down.
Now, when you mix, get a proper balance and if needed, at the end you can boost the total level until it peaks at around -1 or 2dBFS. FWIW, this is your file, with a heavy limiter to tame the peaks, then boosted. I can't change the mix, but it's not a microphone issue.
View attachment 151586
Now my question... if you fire up MediaPlayer or Audacity and play a commercial track from a CD is the volume low? Was your friend's track low? If both of those are yes, then you either have an issue with the Motu, or the way it is connected. Do your monitors have balanced inputs, as in going from the TRS output of the Motu into XLR inputs, or are you going into a 1/4" unbalanced connection. If the monitor input is unbalanced, you should be using an RCA to 1/4" connection. I don't see a mention of the monitor type.
Do your tracks sound low when you use headphones? With almost any headphones you should be able to get very loud.