I can't reproduce you're numbers at all from the links you gave.
For 2013, I see a total of 4,991,993 Million passenger miles of which 4,306,717 Million miles are categorized as highway, leaving 685,276 for All Other. Almost all of the Other category is Air, so I split those out
There are 32719 Highway Fatalities with 429 Air Fatalities and 1361 Other Fatalities. Of those other fatalities 560 are recreational boating so I removed those:
- Category --- Passenger Miles --- Fatalities --- Rate
- Highway --- 4,306,717 --- 32719 --- 0.007597
- Air --- 589,692 --- 429 --- 0.000727
- Other --- 95,584 --- 801 --- 0.00838
So, on a passenger-mile basis, Other is slightly more dangerous than Highway. I don't know how you calculated your numbers, but this is what I came up with after a quick look. In particular that 76 multiplier doesn't seem reasonable at all.
PS. Sorry about the formatting, I couldn't get an html table to work.