I'm kindof leaning towards altering your fighting styles to be more like the fighting styles in Avatar: The Last Airbender. I don't plan on giving them the small bits of element control they have in the show, but the fighting styles are alot like what you have going here. They only had 4 styles, but still. Mountains - Earth. About stubbornness, and strong stances, and dealing damage. CON matches stat wise perfectly. Water - spirituality. your sea style works great. I'd keep wisdom here. Sun/Fire - Agressive, and powerful. their abilities come from their emotions. CHA all the way. (I may tweak this one to be less about bursts of energy and to be more agressive in my game). and Wind/Air - about avoidance. Light quick movements, with an emphasis on avoidance and number of strikes. I love the idea of cloudwalk. it's awesome. For these guys I'd go Dex.
I know these aren't exactly what you were imagining, but they're all based on actual martial arts styles. Earth/Mountains would be based on Hun Gar (you could even call it Hun Gar). Fire/Sun would be based on Northern Shaolin KungFu. Water/Sea based on Tai Chi. and Air/Wind would be based on Bagua.
I dont really like your heavens styles. I like the abilities, but not the element stuff. I don't think positive and negative energy fit the Idea of a monk that I'm imagining. I love the temporary paralysis angle. Don't like shadowstrike, but I hate all things that cause permanent blindness in D&D they just make me angry because if im blinded I'm dead 2 rounds later. Save or dies suck. for quivering palm, I would change it do doing Con Damage. then a tough character will last longer. Also, some way to cure it should exist. maybe a potion, or a ritual, or some form of accupuncture/accupressure. Aspect of death doesn't fit a martial artist in my opinion. it falls under the same category of weird abilities that don't belong (that you were trying to fix)
I dont think fast movement is necessary for all of them.(maybe not any). Mountains/Earth/(Hun Gar) is about strong stances and endurance. they soak up damage. Water/Sea/TaiChi you reduce the damage by controlling your body movements/flow of energy. Fire/Sun/Northern Shao Lin presently uses burst of speed and other burst things, but I would keep them consistent. maybe give them the increased movement, but really I'd say their style is more of an "end the fight before they hit me" type of style. Air/Wind/Bagua I would make be the one about evasion. I don't just mean damage reduction, I mean total avoidance. Maybe an ability to which lets you cancel out attacks of opportunity before the opponent takes them, or an ability that lets you roll to dodge blows so the target hits nothing but air. I'm not sure what I would do for the heavens styles.
but I would line them up with actual schools of martial arts. I think it would just be awesome. and I don't think I'd give them supernatural energy channeling abilities. I mean it fits the asian mysticism associated with martial arts pretty well, but not really the practical aspect of it, you know? same with the undeath thing.
I'd go with Hun Gar instead of mountains, Northern Shao Lin instead of Sun, Tai Chi instead of Sea, Bagua instead of Wind, and instead of the Heavens, maybe base it on another style.
Xingyiquan matches up with your original concept of the sun style. It's all about bursts of power. I prefer the more consistent type of power though, so shao lin sounds better to me.
Chin-Na is the closes I saw to you heavens styles, Pressure point and Joint lock attacks are the focus, but standard martial attacks are there too. It supposedly is the holder of the "Dim Mak" or Death touch.
from a page I found online, "Strengths: An extremely well rounded style with a vast array of techniques that are effective against many types of opponents.
Weaknesses: This style is so replete with so many different types of techniques, its mastery takes much longer than other Chinese styles. Also, its techniques are so precise that any mistake by the practitioner in the execution of a technique will mean the loss of advantage of the practitioner. Where other styles might be effective if the technique is a “near miss”, in Chin-Na any miss is catastrophic. " maybe with some attacks, missing could provoke an attack of opportunity. wouldn't that be nasty.
Just some ideas.
and it took some looking, but I managed to pull it off with all chinese styles
Chin Na could be replaced by Jujutsu and Marma Shastra (neither of which are chinese). the Chin Na alternatives have parts of Chin NA, but not all of it. Marma Shastra is the pressure point one, and Jujutsu is about joint locks and throws. and neither of those two are very good with strikes with the hands or feet for punches and kicks and the like.