I think misc skills increase at the same speed as major and minor skills.
not true. major is at 0.75, minor at 1.00, misc at 1.25
I believe the above behavior is governed by the fSpecialSkillBonus game setting. By default it's set to 0.8, which I assume means that specialized skills take 80% experience to increase compared to non-specialized skills.
that counts too, yes. so specializing will again make increases easier.
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=6083 - there's a useful overview for gmsts