A couple of years ago I gave Shuckums a good review, but the last time we were there, we had a bad experience but assumed it was an "off night".
To charge an automatic gratuity for 5 people is unusual in my opinion (6 or more normally), but tipping should always be optional if the service is deplorable & you complain to the management. To have the manager laugh at you is unacceptable, but to refuse to give you your change back sounds like theft to me. Are the owners on an extended cruise or something?