Measure Numbers all messed up.

simply drag a clef from the palette. And change the height of the sounds accordingly.
http://musescore.org/en/handbook/clef

Why would you want to get rid of that? It is just a G-Clef one resp. two octaves higher, so you don't end up with way to many ledger lines, or a wrong pitch on playback. These are the right clefs for these instruments. just like the f clef with the 8 below for the double bass

I would guess that people who play piccolo are very used to seeing that clef, as it used in maybe half* the published music of the past few decades or so. It is used to indicate that the actual sound is an octave higher. The other half of the published music uses regular treble clef and just assume it is "known" that it sounds an octave higher - just as for transposing instruments like Bb clarinet where it is "known" that it sounds a major second lower. So you have a choice - either use the treble-8va clef like maybe half the music in the world, or change it to regular treble clef but then select everything and drop it down an octave for display purposes (while concert pitch is turned off) and then go to staff properties and change the transposition to "octave up" to get it to play back correctly. Easier to use the treble-8va clef as far as I am concerned, and like I said, people who play piccolo or conduct score for wind isntruments will be quite familair with this already. It really doesn't change anything for them anyhow. Either way, they finger the notes exactly the same and they know the music sounds an octave higher than written. It's just a question of whether there is an explicit "8" on the clef to remind everyone of that or not.

*No, I don't know the actual percentages, but I'm guesisng it isn't too far from 50/50, depending on how far back in time you look.

Or, at least, start a new thread, as it has nothing to do with the original poster's inquiry in this discussion.