Does this patent stop anyone modifying board games?.
First, this is a patent application, not a patent.
The objective of the patent is described in the Background section, specifically, paragraph 5 and 6:
 Sometimes a game becomes less interesting and less enjoyable to a player as it becomes more familiar to that player…
 However, game modification apparatus and processes disclosed herein can help make familiar games more interesting, …
The scope of the application is specified in the claims. Again, this is a patent application, so the claims may change during the examination process, but generally the claims cannot be expanded beyond what's originally written.
The application has three independent claims. Each claims began with the preamble
Game modification equipment for modifying how a variety of preexisting games are played by modifying aspects of play which are shared by various games,…
We should reasonably assume that means the board by design allows you to play more than one game with it.
Each independent claim also includes reference to a "modification instruction". So it is quite apparent that the claims are intended to cover boards as manufactured, not any personal modification by individual persons.