MIDI-Import, Key signatures, Measure changes, tuplets, dividing staffs

Hello everybody, I am new here.
Every item marked with "+ + " at the beginning raises a question.
I am running MuseScore Version 0.9.4, Revision 1518, downloaded this week.
In Cakewalk Sonar 4 "Producers Edition" I had created a larger piece of which I need to have a printed score.
As I had encountered many troubles with Sonar's scoring (limited number of possible dynamic entries, wrong display of tuplets larger than triplets) I had found MuseScore.
So what I am doing is:
1.) I run the application and close the demo.
2.) I click "open" --> browse to the "Cakewalk Projects" and select the .MID version of my piece.
3.) I am prompted to select "shortest note" and select 1/64.
4.) The tune comes up. The title does not appear, and between staff 1 and 2 the subtitle is displayed. No trouble, I move it on top over first staff. I cerated a new page with the title.
+ + 5.) The strings of course need much space. I had, in the original .mid-file in Sonar, one track for the strings. Can I divide the staff "strings" in 2 parts to have a G-clef for the upper half, and a F-clef for the lower? (I'd feel comfortable in the dividing point is at c'.)
6.) Some instruments are in the wrong clef, for example in G-clef, when they should be in F-clef.
7.) I select "Create / clefs" and drag the appropriate clefs to the systems. Notes are adapted to the new clef.
8.) The imported file is in a-minor. The imported and created score file has the property "sounds as notated". Some of the staffs appear without key signature, which is correct for the key a-minor. Others however have the signature of c sharp minor, and the notes therein are enharmonically changed: f is written as e sharp, e is written as d double sharp, c appears as b sharp and so on.
9.) I select "create / key signatures" and drag the appropriate signatures (that is, no sharps, no flats) to the staffs with the wrong signatures.
+ + 10.) The sharps disappear, but the notes are still being displayed with the former enharmonic values. Do I have to adjust every single note now?
+ + 11.) Later in the piece I have a cadence for which I had chosen in the original .mid-file (in Sonar) irregular measure changes: 17/16, 15/16, 5/8, returning then to the normal measures. Going to that place in the score I find the measure changes are at the right place, but the contents of the measures are completely wrong after the 2 measures in 17/16.
The values in the measures are then: 7/8 instead of 15/16, 7/16 instead of 5/8, 17/16 instead of 4/4. How can I correct that?
+ + 12.) Then follows a passage with tuplets. There should be 2 triplets, followed by 4 1/16-notes, followed by a quintuplet (5 1/16 in the time of 1 quarter), then a septuplet (7 1/16 in the time of 1 quarter). Instead, there are sometimes chords created of 2 notoes which originally follow each other. How to adjust that, please?
+ + 12a) Originally, there were a lot of triplets in the bass line, as well as in a part of the drumset. Non of them reappears in the score. How to rearrange that?
+ + 14.) The drum notation: I have the same trouble that the note forms can be selected, but they are not changed in the score.
Any suggestions are welcome. Thank you.