Right now I'm a senior in highschool and in order to graduate, we have to do a senior project. I'm going to do a music project with this girl who sings plays piano and flute. So in order to speed up the writing process, I'm going to learn how to play some basic flute stuff to get concepts put down and then she will be able to really spice things up.
Also, like 3 days ago, I was with me ex-band mate and I look on his floor and I see this tiny little gig bag. I asked him what it was and he told me it was a ukulele. So I grab it out, tuned it the best I can, and we started walking around town and I was just playing it turning heads. In the "experimental" uke tuning I wrote 1 song for my project. I'm telling this because I picked it up with zero experience, figured out about 10 chord shapes with variations, and also how non chord notes mesh together inbetween strings. Unfortunately, it turns out two of the strings were tuned wrong, so after re-tuning to the correct tuning, I'm just looking at a chord chart and playing along with songs.
The whole shortening measures, I don't know if its technically incorrect, but I play concert/jazz band and I've seen shortened/elongated measures, besides, if you're writing it for yourself, then it doesn't really matter as much, especially when you're trying to conserve lined paper.
The second question, do you mean like which notes are sharp in the key of say G? Here:
How To Tell What Major Key A Song Is In Quickly & Easily This might offer some assistance.