Oh and to give my limited knowledge to the questions...
1) Too vague. Muddiness can come from a huge number of things so this is not something that can be answered easily.
2) EQ out the low end using a low pass filter, do a notch filter sweep (create a very narrow band with the Q knob, crank up the gain on it then sweep it back and forth through the spectrum to find where the ring is... then turn it down). Put a compressor on it with a somewhat slow attack so it doesn't kill the crack of the snare then use a slowish release time so the compressor doesn't turn off before the snare hit is finished ringing out. Play with the threshold to figure out what level is need to make this sound natural.
3) Boost the bottom end and do a low mid scoop just after that low boost. Then do that notch filter/sweeping technique in the hi mid range to find the beater click and keep that slightly boosted with a slightly curved Q on the band.
4) Use a limiter/gate before it hits the compressor and set it so the gate closes before you hear the bleed.
5) Again too vague
6) You gotta find the right way to EQ and pan each. Also learn about delay, reverb and the Haas effect to bring more depth to the elements in your mix.
I'm still learning myself so don't take that as gospel and some of it might be completely wrong but that's how I've been interpreting things so far.
Just keep reading, watching, asking and most importantly experimenting. Good luck.