Sharing personal experience.

I once relied only on gels (powerbar, goo and clif) , it tends to make my stomach acidic after 4 + hours causing me to slow down on a race or long runs. Experimented with other stuff during long runs - any combination of mixed nuts, trail bars, gels, dark chocolates (yum!), dried fruits (dates, figs, raisins). I even tried making my own gooo from rice+honey+molasses, which I place in a squeezable container - same thing with gels.

Nuts and dried fruits were good at keeping the energy up for hours and no problem with digestion. I found this way better than gels. But tends to be painful on the jaw, constantly chewing for hours on a long run or a race. Also be sure you have enough water, for potential choking. I've read Gordy Ainsleigh and some early mountaineers use trail mix -where I got the idea.

I agree with the 300 calories an hour myth. Yiannis kuoros (Ultramarathon great) was found to consume almost same amount of energy he used in the Sydney to Melbourne race (about 600+ cal per hour. Mark Allen recommends to train the gut to digest 500 calories an hour.

Tim Noakes findings says the bonk is based on sugar/calorie deficiency on the body and not the lack of water intake.

I stopped counting calories, electrolyte and water intake on races because this is too confusion. I am now running eating and drinking based on feel. If i feel hungry or low I eat and eat more. I dont drink when not thirsty just to keep up with a400 ml hour S cap suggestion. And its working better for me!

It could be as simple as overheating on a hot day.

 

For the sodium intake, the average in hot weather on very long runs (as measured in several studies) is 600 mg of sodium per hour, a good range is anywhere between 500 and 1000 mg per hour (it can vary a lot between different runners).

 

For calories, the 300cal/hr is a myth and does not hold up when measuring actual caloric intake during ultra races. Most runners need more than 240 cal/hr on average in a 24 hour period, and the probability of finishing a 100-miler is best with a caloric intake around 250 to 400 cal/hr. That said, it does not mean that these values apply directly to you, so best use your own experiences with food, water and salt, and take the average values only as a general guideline.

 

The ear symptoms might be caused by a lack of blood supply due to overheating or dehydration, or low blood pressure (low blood sugar may be one cause for that).

I am the opposite - I track calories and hydration to make sure I do not get behind, once you get behind it is a bitch to try and catch up.  My crew (Wife) will track the calories on a notebook.  The only time it gets tense is when I took endurox (300 calories) say at 11:55, then 2 gels from 12-12:59 and she is hounding me to eat.  I aim for a minimum of 300 / hr, trying to hit 400-500 average.

Drinking - I find since my Endurix has 12 ounces of liquid and I get 20 ounce bottle with each gel (Sometime I only drink 12-15 ounces) - Although hydration is tracked, it is not an issue to get 30+ ounces per hour.  Even with 30+ ounces and 500 calories per hour, I usually drop 10+ pounds in the 1st 12 hours.