(a) Lingo is pretty dated (80s wealthy would-be hipsters, and people who pine for the British Empire being the only ones I have heard using it).
(b) It's kind of racist (it's dismissive of the manner of speech it is applied to), and it doesn't just mean "jargon", it means any manner of speech, including foreign language or other dialect one wishes to dismiss.
(c) There is absolutely no way it is more professional than "jargon" (which is a perfectly normal word).
The real question is why you think there might be a problem with using the word "jargon".
The second and third examples are more formal than the first, and slightly more suitable for use in a “formal letter”.
All of the examples are acceptable in conversation. In a formal letter, one probably should use more-precise wording. In particular, “need to”, “at least”, and “day” should be clarified or differently expressed.
For example, “need to” might be expressed as any of “The terms of your contract require you to ...”, “I'd like for you to ...”, or “You will benefit more if you ...”. “Day” might refer to a workday or shift, a calendar day, etc.
“Do at least this much” might mean “On average do this much”, or might mean “Never do less than this much, on any day”. For example, one might write “You are required to respond to at least 100 messages per shift, on average” or “You are required to average at least 100 messages responded to per shift” or “During each shift you must respond to at least 100 messages”, depending on intended meaning.
Best Answer
Of the three options, ‘of’ is the least common, as bib mentioned. I cannot think of a particular situation where it would be more appropriate than ‘from’ or ‘in’.
‘From’ and ‘in’ have slightly different meanings:
If you were comparing actions, rather than entire characters, ‘in’ would definitely be far more natural than ‘from’—e.g., “He eats a slug and then immediately throws up, reminding me of Ron in Harry Potter”, where the reference is not to Ron Weasley as a complete character, but rather to the specific setting/scenes where he is unfortunate enough to end up vomiting slugs for half a day. ‘From’ here would have been somewhat awkward, indicating that Ron’s entire personality reminds you of someone eating a slug and then throwing up.
If you are simply comparing characters as a whole, however, both work fine, although ‘in’ gives the vague impression that there is something more or less specific in To Kill a Mockingbird that makes the character you’re describing here remind you of Dill.