I'm desperately trying to get the pre-built date range filter to work the way I need it to.

Specifically, I have been asked to provide detail for how many project hours are expected to be spent within 30 days for resource allocation. My superior does not use MS project, but rather a crude excel spreadsheet for his own tracking.

No matter how I format the date range, I am given the entire duration of work left to be performed for the entire task. For example, if I have a task spanning 6 weeks, and I am only supposed to provide detail for 30 days, the duration still shows the entire duration, even the hours outside of the 30 days.

Does anyone know of a way to rectify this? I'm at a complete loss.

The time filters in MSP tend to relate to task start and finish dates, and will not cut a task off- if a task starts/finishes within the specified time frame, then the task will be shown completely. As far as I know, there is no way to cut atask up in the way you want using these filters.
However, that doesn't mean it cant be done. As you superior is using Excel, I would suggest using the same output type. I use MSP 2010, but I assume that 2013 is fairly similar- sure someone can assist if the buttons are different.
Go into visual reports, under the Project tab, and choose either "Resource work availability" or "Resource work summary"- one of these will give a result that is most likely the one you want, but will need to try both to see which is best for you. select the chart and choose the level of usage- I generally go weeks, as days can take a while, but again depends what you want- then click view. In the excel sheet that comes up, you can change date ranges to actual dates (non task dependent) and show whichever work attribute is suited (generally "work" will give actual or predicted hours). Filter by date range and resource to the level you want, and you have a nice graph that should appeal to the excel minded person who wants to keep it simple.

If this doesnt give what you want or you need more help with anything, let us know- sure others will have other solutions too

For a quick look - try the Task usage view and zoom the timescaled portion (right side) out to show months.