Of course, not all of my songs are in F minor. I transpose the melodies after I write them. Ableton has a useful MIDI effect called pitch that you can apply to any synth and it will do this for you.
3) I recommend adding pitch bend, portamento, vibrato and velocity variations to your melodies. They help break the monotony and add a lot of feeling. You can hear pitch bending on both the lead synths and the bass in my track Secrets with Tiesto. Also, be conscious of the length of all of your notes and how that affects the rhythm you create. This can be very important.