迷惑 and 困惑 can both be verb or adjective
迷惑 = to confuse (deceive someone and make him confused)
困惑 = to confuse (trap someone in a confusion)
We use 迷惑 for "to confuse" to emphasize the deception part
Example: 用妖言迷惑群眾 (妖言惑眾) - use lies and rumors to deceive and confuse the public
We use 困惑 for "to confuse" to emphasize the trapping part
Example: 各人不同的口供困惑了調查人員 - Everyone’s different stories confused investigators (trapped them into a confusion with different stories- but there may or may not be deceptions)
弄混，搞亂，搞混 are just different versions of shortened form of "弄/搞 (make-v) 混亂 (confusing-adj)"
e.g. 搞亂局面 = 使局面混亂 (make situation confusing)
1) English: "What you just said confused me."
2) English: "I was confused by what she did."
4) For the preceding answers, are there any differences between Mandarin and Cantonese?
The grammar are the same, the terms may be different.