There are features that Arc gets for free when implemented on top of Scheme that may be hard on other platforms such as full continuations, tail calls, and the numeric tower e.g. exact rationals. Since you sound like you're interested primarily in a practical system (DirectX game development), you can avoid getting bogged down by not worrying about the features you don't need. (For example, you might choose to have this implementation of Arc only support escape continuations).
To keep the complexity down and the progress encouraging, I find it helpful to work on an implementation as a series of steps instead of doing everything all at once. For example, you might start by implementing just enough of the runtime so that you can load the first form in arc.arc, do. Then implement just enough more so that you can implement safeset, and so on.