Im sure others will pick holes in this :-) - but here goes

1) I would leaderboard uniquely with best score - I.E. I play 100 times - my best score is in the leaderboard list at the top of the results page. Below that all of the entries are displayed - people should always be able to see how many times I played and check out my replays etc.

2) Yes - but carry on recording all the entries - just have a leaderboard at the top of the results based on player limit or top 10.

3) Well - it depends how you see the two measures. I wouldn't mess with exponential scoring there could be all sorts of issues with 'long' tournaments when the winner gets stupid amounts of points.

From what I see so far ----

EXP should equal skill?
GP should equal effort / participation?

So if I play lots of games my exp 'gradually' increases but if I win tournaments my exp is 'bumped' quickly - good players should exp level up quickly- or I get some other badge of honour (Gold / Silver / Bronze -- etc etc) - The EXP bump could be based on map type - e.g. Easy 1st place I get 10 EXP - Hard 1st place I get 100 EXP etc.

If I play lots of games my GP grows at a set amount for each play - no multipliers or bonuses required - no extra GP for hard maps - my ranking in tournaments shouldn't bump my GP - except for GP earned from replays due to my epic win.

4) Yes - if EXP is a set bump based on map type. I.E. a good player shouldn't be able to pitch up at an easy tournament and knick all the EXP from the new players. Max level for entry comes into play here. Also - maybe if I am a level 1 player playing a level 10 map I get 1000 EXP - but if I am a level 10 player on a level 1 map I get 10 EXP. (you get the idea)

5) I guess this is a little tricky - would I want to go into a tournament I could never get 1st place in? I guess it will settle down into quick fire type games that cycle every 4 hours vs. epic 200 level boss only juggle for hours every point counts tournaments that could be open for weeks -- I think you need to look back at the play data after a few months to go back and tweak things.