Changing the hands, run them under hot water for a minute or so, they should pop out easily.
As for making the joints tighter, try squirting a little elmers school glue into the joint. Work the joint every few minutes to get the glue into the joint. You can also use super glue instead of Elmers school glue, but you have to be careful NOT to solidify the joint. If it's a ball joint, pop off the part and add a very small dab of super glue around the ball part. Wait for it to dry and put the limb back on. If it's still too loose, repeat this step until you have the right amount of tension in the part.