Sweets

I'm afraid I can't help you in that regard, as I too have no idea where to get them outside of ripping them from the game yourself.

I assume you mean to knock them into the air.
 
in which case add fall = 1 to the hitdef, and set your ground.velocity = -1,-5
change -5 and -1 to desired distance.

Audacity.
Literally open your .mp3 up and resave as .wav.
Heck, you can even batch convert to .wav.

you can use a bindtotarget code or a posset code.
[State 0, BindToTarget] type = BindToTarget trigger1 = !time time = 99 ID = -1 pos = 0,0,Mid or [State 0, PosSet] type = PosSet trigger1 = 1 x = target,pos x y = 0  

Your helper is already simple, it just need some fixs
 
;---------------------------------------------------------------
;Projectile helper
[statedef 222]
type = A
movetype= A
physics = n
ctrl = 0
anim = 230
sprpriority = 2
velset = 0,1
 
[State hitdef]
type = HitDef
trigger1 = !time
attr = S, NP
hitflag = maf
animtype = Medium
damage = 200,0
guardflag = MA
pausetime = 1,1
sparkno = s1
hitsound = s5,2
guardsound = s6,0
ground.type = high
ground.slidetime = 0
ground.hittime = 0
ground.velocity = 0
air.velocity = 0,0
 
[State to exploding state]
type = ChangeState
trigger1 = movecontact
trigger2 = vel y > 0
trigger2 = pos y > -vel y
value = 223
 
;---------------------------------------------------------------
;Exploding projectile
[statedef 223]
type = A
movetype= A
physics = n
ctrl = 0
anim = 240
sprpriority = 2
velset = 0,0
 
[state safe pos ground]
type = posset
trigger1 = !time
trigger1 = pos y > 0
y = 0
 
[State end]
type = DestroySelf
trigger1 = !animtime

I think this trigger is the one that doesn't work properly. It tries to resolve the condition pos y > 5, then divide it with vel y, and then check if the result is greater than -5. Its odd if you only want to check if the helper hit the ground.
 
You can use
trigger1 = pos y >= 0
 
or
trigger1 = vel y > 0
trigger1 = pos y > -vel y
 
as alternative to that trigger. First one is simpler, but can allow the helper go below the ground very often. Second one is what I'm using and works pretty well, took it from here. Anyway, on state 224 you're resetting its pos y to 0, which is great because you're preventing it to go below ground.
 
Keep in mind that multiple helpers are generated every tick on state 221.
 
 
Edit: Or you can just replace / with && and it will work fine :P