#1
Would you consider it bad technique if I didn't sweep up the neck? Like, I can do the downward motion very cleanly, but when going back up, I don't use my picking hand at all, I just use my fretting hand to hammer on the notes. I mean, you can't tell if listening, but it kinda bothers me.
Gear:
Jackson Pro Series DK2 Dinky (Eerie Dess Swirl)
Ibanez XPT700 Xiphos (Chameleon Red) =D

Crate FXT65 amp with 3-way foot switch
Ibanez Weeping Demon Wah Pedal
#2
You should learn how to sweep correctly up and down the neck before you try experimenting.
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Jackson SLSMG Ibanez Jem7v Jackson SL3

Line 6 Spider Valve 212

Ibanez Weeping Demon Wah
#3
If it sounds okay, then it's probably fine. I would still learn how to sweep up though, just to work on the fluidity of your picking hand.
Ibanez RGA121 | ESP LTD H-1000
Axe-FX Standard