If we stick to your proposed answers:

Je connais un peu de français.

is the best.

But I feel the most idiomatic would be:

Je parle un peu (le/de) français.

or

Je sais parler un peu (le/de) français. / Je sais un peu parler français.

Note that connaitre cannot be followed by another verb, so no hesitation in this last case.

As noted is this other answer je sais le français would have been used until the early 20th century but saying it nowadays would really sound outdated.

If you discuss around something in French, among people who can’t read or understand :

Je connais un peu le français.

Using the verb "savoir" needs another verb after:

Je sais parler le français.
Je sais lire le francais.

Using the verb "connaitre" is more around knowledge, so to know about French is "big" and can touch the food, habits and not only language… It can be something like this with "connaitre":

Je connais un peu la grammaire française, mais je ne sais pas l’écrire correctement…

I know some about french grammar but can’t write it correctly

Je connais bien la cuisine française (i know well french cooking)

Hope it helps some.

That link https://french.stackexchange.com/a/59/358 should help you too.