2. Mid height with a bit of a tilt would probably be your best bet, you'll be able to hear yourself better (try to visualize the sound waves pumping from the speaker. If you're having trouble hearing yourself, move your head directly into the path of the waves. This is where the tilting comes in handy.
~~ ~~~
EX: ~~ (you)~
~~~ ~~ (<-waves)
(speaker)-> \ ~~ ~~ ~~
\ ~~ ~~
\ ~~
This will also ensure that the crowd hears the (refined miced & eqed) sound from the PA speakers more than your amp, making mixing easier on the sound guy.
3. Experiment heavily with different mic placements. Personally, I perfer to mic a little back and to the left of the speaker (but I'm using a closed back 4x12, so your results will more than likely differ). The best way I've found to look for "sweet spots" is to put on a set of studio headphones from the board, have someone play your guitar, and move the mic all around. Just have them stop where it sounds best. Also, make sure the gain on the board isn't too high. You want the distortion to come from the amp, not the mic. You'll have a bad tone and lots of feedback if you've got that mic too hot.
4. You're tone settins are subjective to your own personal taste, but try to have your tone fit the band's mix well. Be especially careful with the highs and presence. If you don't have enough of them, you'll get lost in the mix, but if you have too many you'll screw up the rest of the band's sound. Having too many highs/presence is a common tonal mistake that guitarists new to the band thing make. Also, since you're the lead player, you may consider adding a just a little bit more mids. They'll make your leads stick out a bit more. An eq or seperate distotion pedal comes in handy here, because you can just kick one of them in when you do a solo, giving you more mids and a volume boost when you need them, then letting you return to your normal rythm sound/volume.
If you have any other questions, feel free to ask. A good tone and mix can make or break a gig.