First :20 in the song you're off grid. that could be a tempo map issue or just your note alignment. but if you play it, the player will feel a bit "off" when hitting those notes. which makes it seem like you missed some. seems like the tempo syncs up at :22 though.
:40 - you come in too late or you haven't charted enough notes. go really slow through this area and you'll see you have guitar playing before your first green note.
1:13 - it's a three strum chord progression, you have it mapped as singles
2:08 -2:16 - this section doesn't line up with the guitar that's playing. Again, slow it down to hear your notes aren't hitting in time with the music. they might be the right pattern, but they are out of sync. Good transition though to the follow up solo. Make sure to mark that solo as a solo. :-)
Based on your comment I'm guessing you're only doing 5-lane keys? It's sometimes better to author pro keys as they are played, then start taking notes away so they are able to be played with one hand only. Most the time, that means eliminating what the left hand plays. So once you have that, you then do a conversion for 5-lane keys. So basically, you want to emulate as close to playing real keys as you can. If a keyboardist is hitting three notes then author three notes. I wouldn't just make them three notes without it being like you'd play on an actual keyboard.
I'd also check out that section on the docs again and read it over. It took me quite a while to get authoring keys down (and I still don't profess at being an authority with it) so keep at that one.
For your other comment regarding files:
The midi file will only contain the tracks you are creating and will NOT include any of your audio files. If you aren't using multitracks, you'll have audio files that you load up in MAGMA (the main audio track with count in, a silent track, and your dryvox track(s)). These will be compiled INTO the CON file that is used in game. This will compile ALONG WITH the midi file you create. So think of these things separately. MULTIPLE audio files, ONE midi file.
And then lastly your credit:
You really only need to credit when someone is contributing a chart (keys, guitar, bass, drums, venue, etc.). You don't need to credit people who help you along the way. You can thank them if you wish, but it's not required. If someone helps you directly author a track, you should credit that.
Hope that helps and keep at it!