In contempt the judge can fine, jail, or both. And there is no set sentence on contempt charges; the judge can keep you there as long as they like if you continue to refuse to comply with the court order. People have been jailed for months on contempt charges. There was a case where a guy spent 15 years in jail for refusing to comply with a court order.
I was just polishing up on this and you are pretty much right which is surprising in the answer, however, there are grounds for appeal if you could prove that any “prolonged” (undefined) detention is “unreasonable” (undefined).
I would imagine that being (basically) compelled to testify against yourself in a prosecutorial fishing witch hunt and then being found in contempt for refusing to participate in your own prosecution may be considered as unreasonable to a few judges... but you would have to find the right one.