The fellow should be on his trip by now. I hope we hear from him when he is done.
Obviously he will not carry 70 pounds, travel 12 miles every day and "fish and trap" along the way on an unmaintained trail that likely is overgrown. But I would hope he does a little, adjusts his plan, and continues. Given his time limit (one month) he will likley not make the entire trail, but would have an adventure and learn a lot. The experience will teach him more than anything we can say.
Since I have done some "fishing and trapping" myself, those activities do not net much unless you spend a lot of time. Once caught, any fish or animal would have to be skinned, cleaned and preserved. I doubt much of this will actually be done.
I carried the weight on NOLS mountaineering courses. Some days we traveld 10+ miles, many we "base-camped" and climbed, some we traveled half days and did classes half days. Some miles were on trails; some not. Thankfully, the food weight became 2 pounds less each day. We got reupplied by horse packers about every 15 days. Our "base-weight" was about 40 pounds (at the end of 30 days, when we instructors walked out we did 25 miles in a day). So, you are right in that these weight packs are not what you want if trying to make miles every day. But the short days and long days tend to average out- with 12 miles on the average definetly optomistic!