Until you know for sure if there is a bolt detent for the stock bolt in the fore stock, it is cheap insurance to just remove the fore stock before you turn that butt stock bolt. Once the front wood is off you will know for sure.

Otherwise there is a real danger of splitting the back end of the fore stock.

Chances are that there is no square ended butt stock bolt, but why gamble?

Usually, tightening the butt stock bolt will get rid of the wobble. If the butt has wobbled a lot over time and has worn away in the butt socket, that can be fixed too.

Don't go anywhere near that loose butt stock with epoxy compound. There are other ways to fix it as per the period armourer's methods.