I agree with Bill on both points. The word you are looking for is 'tease'. We use it to mean 'make fun of', but in a playful or affectionate way. And yes, 'sb' is (1) meaningless (2) an obvious sign that you're a Russian speaker. Only Russians think that 'sb', 'smth' are meaningful in an English sentence. Nobody else uses these supposed abbreviations, and nobody else understands them.

I would say "I'm just messing with you". This is a very common way to say it in American English, and isn't associated with old people or anything. I slightly disagree with the others saying that nobody understands "sb". I understood it, and to me it just looks like a younger person (not a Russian) wrote it if those abbreviations are used. "I'm just giving you a hard time" is also common, as another person mentioned. The other examples you listed at the end of your question are not very common and would sound strange for a non-native speaker to say.

Expressions such as "wind up' and "bait" have a stronger meaning than you need. Both words suggest that you want to get the other person angry. Goad, harass and pester also have a negative association. Parents, in a friendly way, would KID or TEASE their children. They might say, "I'm just kidding you" or "I'm just teasing you". Some other expressions might be, "I'm just poking fun" or "I'm just horsing around". Hope this helps

In American English we usually say, “I’m just giving you a hard time.” Or “I’m just giving you shit.” People who are older than about 60 years old use other phrases. They would say, “I’m just jerking your chain.” Or “I’m just razzing you.”

1) "sb" does not mean anything in English 2) try "tease"