Where can I find more information about my grandfather's crashed B-18a bomber on Mt. Redoubt Alaska?
What is the terrain/glacier situation [on the southeast side of Mt Redoubt]?


The southeast side is all glacier, forming in the valleys formed by previous formative eruptions, which have deepened significantly due to glacier flow. These glaciers do move and churn, so unless the plane crashed on top of one of the prominent ridges then the position of the plane's remains is changed, and they are likely mixed/buried within the glacier.

It's been 75 years though, and while the glaciers sped up during eruptive periods (or melted, as on the north face during the 1989 eruption), the average annual glacier speed is 20 meters per year.  So the wreckage would have moved at least 1.5km down the mountain slope over time, buried under new snow (and occasional ash), and always moving down into the drift glacier.

These reports on Mt. Redoubt's glaciers should provide significant help in determining the location, thickness, and movement of each glacier present:

https://pubs.usgs.gov/wri/1997/4187/report.pdf

https://www.igsoc.org/journal/32/112/igs_journal_vol32_issue112_pg355-362.pdf

In a normal crash if you have the location to within 100 meters it can be found with a simple search, even decades later, even though the plane may have undergone environmental extremes.  In this situation, though, not only will the wreckage have been moved, but it will have been torn apart and spread over a much larger area than the original crash.


  Is landing possible at this location?


You can land on glaciers in general, and these are no exception, but you can't land on the side of Mt. Redoubt any easier than any other mountain.  You may be able to land at the base of the mountain, but you'd have to decide which glacier flow to land on, and as explained below it's unlikely that you will find anything to help you decide which one.

The pilot will have to make the final decision, though, as conditions may vary, not just in the weather, but on the glacier itself.  


  Has anyone seen an accident site at this location?


Only the rescuers would have.  Once consumed by the snow and glacier over years it would have remained only as small parts of the whole.  Any pieces remaining visible to the eye would also act as solar collectors - they would melt the snow beneath them, sinking lower into the glacier, and then be covered by another fresh layer of snow.

I commend you and your father for your dedication to this aspect of your family history, and wish you luck!