Okay, quite a few different things:
1) There are only two notes playing at a time for each piece. Was that the case in the original midi file? I have to imagine that there were more tracks than this.
2) You only need as many tracks as the highest number of notes that ever play at the same time.
That's probably a confusing sentence.
Basically, since this file only has two notes playing at the same time, it's possible to create the song with only 2 tracks instead of 6. Of course, manually reducing the number of tracks can be very tedious, especially in more complex songs. In this case however, you can paste tracks 3 and 4 to the ends of 1 and 2. The same for 5 and 6. The challenge here is to make sure that the next song starts correctly. You have to count your rests and make sure that the tempo markers line up on the left. But once you accomplish this step, the song will be much easier to work with. Additionally, all of those rests in the extra tracks take up a significant amount of room and could be the difference between fitting it onto a sheet in-game or not.
3) Again, in order for the song to work in the game, you have to put the same tempo in each track.
In this MML file, I only see tempo markers for tracks 1, 3, and 5, and they are not at the same locations either.
In music, 'rests' are affected by the tempo just like everything else. Therefore, tracks 3 through 6 still need the marker for 't150' at the beginning, etc. Think about it. If that wasn't indicated, how would the score know how long to pause for? It would just count rests according to whatever the default tempo is.
We're not exactly doing computer programming, but it's still a kind of coding, and sometimes we need to step back a minute and think about what we're actually saying to the software.
4) Once you've got a good idea of how a song is setup and a good handle on how to interact with the piano roll and time stamps, I recommend going to the "track" dropdown at the top, then selecting "optimize" track. Ultimately, all the line indicators, arrows, and other junk at the beginning is unnecessary. At best, they just take up space and at worse, they could mess up your song.
Well, this was about as much as I could do with it.
Before optimizing:
ElderScrollsSuite-bop.mml
After optimizing:
ElderScrollsSuite-aop.mml
Edit:
And here's the in-game file.
ElderScrollsSuite.ms2mml